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Blue is one of the three
primary colours Primary colors are colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printin ...
in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between
violet Violet may refer to: Common meanings * Violet (color), a spectral color with wavelengths shorter than blue * One of a list of plants known as violet, particularly: ** ''Viola'' (plant), a genus of flowering plants Places United States * Vi ...
and
cyan Cyan () is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK c ...
on the
spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
of
visible light Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm ...
. The term ''blue'' generally describes colours perceived by humans observing light with a
dominant wavelength In color science, the dominant wavelength is a method of approximating a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. The dominant wavelength of a given color is defined to be the wavelength of monochromatic ...
that's between approximately 450 and 495 
nanometre 330px, Different lengths as in respect to the Molecule">molecular scale. The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling), is a unit of length ...
s. Most blues contain a slight mixture of other colours; azure contains some green, while
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as
Rayleigh scattering Rayleigh scattering ( ) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scat ...
. An optical effect called the
Tyndall effect The Tyndall effect is light scattering by particles in a colloid such as a very fine suspension (a sol). Also known as Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is inversely propor ...
explains
blue eyes Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. In humans, the pigmentation o ...
. Distant objects appear more blue because of another optical effect called
aerial perspective Aerial perspective, or atmospheric perspective, is the effect the atmosphere has on the appearance of an object as viewed from a distance. As the distance between an object and a viewer increases, the contrast between the object and its backgro ...
. Blue has been an important colour in art and decoration since ancient times. The semi-precious stone
lapis lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, ''lāžward'', lapis lazuli is ...
was used in ancient Egypt for jewellery and ornament and later, in the
Renaissance The Renaissance ( , ) is a Periodization, period of history and a European cultural movement covering the 15th and 16th centuries. It marked the transition from the Middle Ages to modernity and was characterized by an effort to revive and sur ...
, to make the pigment
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
, the most expensive of all pigments. In the eighth century Chinese artists used
cobalt blue Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminium(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Cobalt blue is lighte ...
to colour fine
blue and white porcelain "Blue and white pottery" () covers a wide range of white pottery and porcelain decorated underglaze, under the glaze with a blue pigment, generally cobalt(II) oxide, cobalt oxide. The decoration was commonly applied by hand, originally by brush p ...
. In the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
, European artists used it in the windows of
cathedral A cathedral is a church (building), church that contains the of a bishop, thus serving as the central church of a diocese, Annual conferences within Methodism, conference, or episcopate. Churches with the function of "cathedral" are usually s ...
s. Europeans wore clothing coloured with the vegetable dye
woad ''Isatis tinctoria'', also called woad (), dyer's woad, dyer's-weed, or glastum, is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, ''Isati ...
until it was replaced by the finer
indigo InterGlobe Aviation Limited (d/b/a IndiGo), is an India, Indian airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 64.1% domestic market ...
from America. In the 19th century, synthetic blue dyes and pigments gradually replaced organic dyes and mineral pigments. Dark blue became a common colour for military uniforms and later, in the late 20th century, for business suits. Because blue has commonly been associated with harmony, it was chosen as the colour of the flags of the
United Nations The United Nations (UN) is the Earth, global intergovernmental organization established by the signing of the Charter of the United Nations, UN Charter on 26 June 1945 with the stated purpose of maintaining international peace and internationa ...
and the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
. In the United States and Europe, blue is the colour that both men and women are most likely to choose as their favourite, with at least one recent survey showing the same across several other countries, including China, Malaysia, and Indonesia. Past surveys in the US and Europe have found that blue is the colour most commonly associated with
harmony In music, harmony is the concept of combining different sounds in order to create new, distinct musical ideas. Theories of harmony seek to describe or explain the effects created by distinct pitches or tones coinciding with one another; harm ...
,
confidence Confidence is the feeling of belief or trust that a person or thing is reliable. * * * Self-confidence is trust in oneself. Self-confidence involves a positive belief that one can generally accomplish what one wishes to do in the future. Sel ...
,
masculinity Masculinity (also called manhood or manliness) is a set of attributes, behaviors, and roles generally associated with men and boys. Masculinity can be theoretically understood as Social construction of gender, socially constructed, and there i ...
,
knowledge Knowledge is an Declarative knowledge, awareness of facts, a Knowledge by acquaintance, familiarity with individuals and situations, or a Procedural knowledge, practical skill. Knowledge of facts, also called propositional knowledge, is oft ...
,
intelligence Intelligence has been defined in many ways: the capacity for abstraction, logic, understanding, self-awareness, learning, emotional knowledge, reasoning, planning, creativity, critical thinking, and problem-solving. It can be described as t ...
,
calmness Calmness or, nonchalance is the mental state of Inner peace, peace of mind, being free from agitation, excitement, or Psychological stress, disturbance. It also refers to being in a state of serenity, tranquillity, or peace. Calmness can most eas ...
,
distance Distance is a numerical or occasionally qualitative measurement of how far apart objects, points, people, or ideas are. In physics or everyday usage, distance may refer to a physical length or an estimation based on other criteria (e.g. "two co ...
,
infinity Infinity is something which is boundless, endless, or larger than any natural number. It is denoted by \infty, called the infinity symbol. From the time of the Ancient Greek mathematics, ancient Greeks, the Infinity (philosophy), philosophic ...
, the
imagination Imagination is the production of sensations, feelings and thoughts informing oneself. These experiences can be re-creations of past experiences, such as vivid memories with imagined changes, or completely invented and possibly fantastic scenes ...
,
cold Cold is the presence of low temperature, especially in the atmosphere. In common usage, cold is often a subjectivity, subjective perception. A lower bound to temperature is absolute zero, defined as 0.00K on the Kelvin scale, an absolute t ...
, and
sadness Sadness is an emotional pain associated with, or characterized by, feelings of disadvantage, loss, despair, grief, helplessness, disappointment and sorrow. An individual experiencing sadness may become quiet or lethargic, and withdraw the ...
.


Etymology and linguistics

The
modern English Modern English, sometimes called New English (NE) or present-day English (PDE) as opposed to Middle and Old English, is the form of the English language that has been spoken since the Great Vowel Shift in England England is a Count ...
word ''blue'' comes from
Middle English Middle English (abbreviated to ME) is a form of the English language that was spoken after the Norman Conquest of 1066, until the late 15th century. The English language underwent distinct variations and developments following the Old English pe ...
or , from the
Old French Old French (, , ; ) was the language spoken in most of the northern half of France approximately between the late 8th Germanic origin, related to the Old High German">Germanic languages">Germanic origin, related to the Old High German word (meaning 'shimmering, lustrous').''Webster's Seventh New Collegiate Dictionary'' (1970). In heraldry, the word ''azure (heraldry), azure'' is used for ''blue''. In Russian language, Russian, Mongolian language, Mongolian, Irish language, Irish, and some other languages, there is no single word for blue, but rather different words for light blue (Russian: , ) and dark blue (Russian: , ) (see Colour term). Several languages, including
Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...
and
Lakota Sioux The Lakota (; or ) are a Native American people. Also known as the Teton Sioux (from ), they are one of the three prominent subcultures of the Sioux people, with the Eastern Dakota (Santee) and Western Dakota (). Their current lands are in N ...
, use the same word to describe blue and green. For example, in
Vietnamese Vietnamese may refer to: * Something of, from, or related to Vietnam, a country in Southeast Asia * Vietnamese people, or Kinh people, a Southeast Asian ethnic group native to Vietnam ** Overseas Vietnamese, Vietnamese people living outside Vietna ...
, the colour of both tree leaves and the sky is . In Japanese, the word for blue (, ) is often used for colours that English speakers would refer to as green, such as the colour of a
traffic signal Traffic lights, traffic signals, or stoplights – also known as robots in South Africa, Zambia, and Namibia – are signaling devices positioned at intersection (road), road intersections, pedestrian crossings, and other locations in order t ...
meaning "go". In Lakota, the word is used for both blue and green, the two colours not being distinguished in older Lakota (for more on this subject, see
Blue–green distinction in language In many languages, the colors described in English as "blue" and "green" are colexified, i.e., expressed using a single umbrella term. To render this ambiguous notion in English, linguists use the blend word ''grue'', from ''green'' and ''bl ...
). Linguistic research indicates that languages do not begin by having a word for the colour blue. Colour names often developed individually in natural languages, typically beginning with
black Black is a color that results from the absence or complete absorption of visible light. It is an achromatic color, without chroma, like white and grey. It is often used symbolically or figuratively to represent darkness.Eva Heller, ''P ...
and
white White is the lightest color and is achromatic (having no chroma). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully (or almost fully) reflect and scatter all the visible wa ...
(or dark and light), and then adding
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–750 nanometres. It is a primary color in the RGB color model and a seconda ...
, and only much later – usually as the last main category of colour accepted in a language – adding the colour blue, probably when blue pigments could be manufactured reliably in the culture using that language.


Optics and colour theory

The term ''blue'' generally describes colours perceived by humans observing light with a
dominant wavelength In color science, the dominant wavelength is a method of approximating a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. The dominant wavelength of a given color is defined to be the wavelength of monochromatic ...
between approximately 450 and 495 nanometres. Blues with a higher frequency and thus a shorter wavelength gradually look more violet, while those with a lower frequency and a longer wavelength gradually appear more green. Purer blues are in the middle of this range, e.g., around 470 nanometres.
Isaac Newton Sir Isaac Newton () was an English polymath active as a mathematician, physicist, astronomer, alchemist, theologian, and author. Newton was a key figure in the Scientific Revolution and the Age of Enlightenment, Enlightenment that followed ...
included blue as one of the seven colours in his first description of the
visible spectrum The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optica ...
. He chose seven colours because that was the number of notes in the musical scale, which he believed was related to the optical spectrum. He included
indigo InterGlobe Aviation Limited (d/b/a IndiGo), is an India, Indian airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 64.1% domestic market ...
, the hue between blue and violet, as one of the separate colours, though today it is usually considered a hue of blue. In painting and traditional colour theory, blue is one of the three
primary colours Primary colors are colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printin ...
of pigments (red, yellow, blue), which can be mixed to form a wide
gamut In color reproduction and colorimetry, a gamut, or color gamut , is a convex set containing the colors that can be accurately represented, i.e. reproduced by an output device (e.g. printer or display) or measured by an input device (e.g. cam ...
of colours. Red and blue mixed together form violet, blue and yellow together form green. Mixing all three primary colours together produces a dark brown. From the Renaissance onward, painters used this system to create their colours (see RYB colour model). The RYB model was used for
colour printing Color printing or colour printing is the reproduction of an image or text in color (as opposed to simpler black and white or monochrome printing). History of color printing Woodblock printing on textiles preceded printing on paper in both Eas ...
by Jacob Christoph Le Blon as early as 1725. Later, printers discovered that more accurate colours could be created by using combinations of cyan, magenta, yellow, and black ink, put onto separate inked plates and then overlaid one at a time onto paper. This method could produce almost all the colours in the
spectrum A spectrum (: spectra or spectrums) is a set of related ideas, objects, or properties whose features overlap such that they blend to form a continuum. The word ''spectrum'' was first used scientifically in optics to describe the rainbow of co ...
with reasonable accuracy. File:AdditiveColorMixing.svg, Additive colour mixing. The combination of primary colours produces secondary colours where two overlap; the combination red, green, and blue each in full intensity makes white. File:Closeup of pixels.JPG, Red, green, and blue
subpixels In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, pixels are the sma ...
on a
liquid-crystal display A liquid-crystal display (LCD) is a flat-panel display or other Electro-optic modulator, electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liq ...
. On the HSV colour wheel, the
complement Complement may refer to: The arts * Complement (music), an interval that, when added to another, spans an octave ** Aggregate complementation, the separation of pitch-class collections into complementary sets * Complementary color, in the visu ...
of blue is
yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...
; that is, a colour corresponding to an equal mixture of
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–750 nanometres. It is a primary color in the RGB color model and a seconda ...
and
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...
light. On a colour wheel based on traditional colour theory ( RYB) where blue was considered a primary colour, its complementary colour is considered to be orange (based on the Munsell colour wheel).


LED

In 1993, high-brightness blue LEDs were demonstrated by
Shuji Nakamura is a Japanese electronic engineer, inventor of the blue LED, a major breakthrough in lighting technology, and recipient of the Nobel Prize in Physics in 2014. Nakamura specializes in the field of semiconductor technology, and he is a professo ...
of Nichia Corporation. In parallel, Isamu Akasaki and
Hiroshi Amano is a Japanese physicist, engineer and inventor specializing in the field of semiconductor technology. For his work he was awarded the 2014 Nobel Prize in Physics together with Isamu Akasaki and Shuji Nakamura for "the invention of efficient b ...
of
Nagoya University , abbreviated to or NU, is a Japanese national research university located in Chikusa-ku, Nagoya. It was established in 1939 as the last of the nine Imperial Universities in the then Empire of Japan, and is now a Designated National Universit ...
were working on a new development which revolutionized LED lighting. Nakamura was awarded the 2006
Millennium Technology Prize The Millennium Technology Prize () is one of the world's largest technology prizes. It is awarded once every two years by Technology Academy Finland, an independent foundation established by Finnish industries, academic institutions, and the st ...
for his invention. Nakamura,
Hiroshi Amano is a Japanese physicist, engineer and inventor specializing in the field of semiconductor technology. For his work he was awarded the 2014 Nobel Prize in Physics together with Isamu Akasaki and Shuji Nakamura for "the invention of efficient b ...
and Isamu Akasaki were awarded the
Nobel Prize in Physics The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
in 2014 for the invention of an efficient blue LED.


Lasers

Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word ''laser'' originated as an acronym for light amplification by stimulated emission of radi ...
s emitting in the blue region of the spectrum became widely available to the public in 2010 with the release of inexpensive high-powered 445–447 nm
laser diode file:Laser diode chip.jpg, The laser diode chip removed and placed on the eye of a needle for scale A laser diode (LD, also injection laser diode or ILD or semiconductor laser or diode laser) is a semiconductor device similar to a light-emittin ...
technology. Previously the blue wavelengths were accessible only through
DPSS A diode-pumped solid-state laser (DPSSL) is a solid-state laser made by pumping a solid gain medium, for example, a ruby or a neodymium-doped YAG crystal, with a laser diode. DPSSLs have advantages in compactness and efficiency over other typ ...
which are comparatively expensive and inefficient, but still widely used by scientists for applications including
optogenetics Optogenetics is a biological technique to control the activity of neurons or other cell types with light. This is achieved by Gene expression, expression of Channelrhodopsin, light-sensitive ion channels, Halorhodopsin, pumps or Photoactivated ade ...
,
Raman spectroscopy Raman spectroscopy () (named after physicist C. V. Raman) is a Spectroscopy, spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Ra ...
, and
particle image velocimetry Particle image velocimetry (PIV) is an optical method of flow visualization used in education and research. It is used to obtain instantaneous velocity measurements and related properties in fluids. The fluid is seeded with tracer particles whic ...
, due to their superior beam quality. Blue gas lasers are also still commonly used for
holography Holography is a technique that allows a wavefront to be recorded and later reconstructed. It is best known as a method of generating three-dimensional images, and has a wide range of other uses, including data storage, microscopy, and interfe ...
,
DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, thymine, cytosine, and guanine. The ...
,
optical pumping Optical pumping is a process in which light is used to raise (or "pump") electrons from a lower energy level in an atom or molecule to a higher one. It is commonly used in laser construction to pump the active laser medium so as to achieve popu ...
, among other scientific and medical applications.


Shades and variations

Blue is the colour of light between
violet Violet may refer to: Common meanings * Violet (color), a spectral color with wavelengths shorter than blue * One of a list of plants known as violet, particularly: ** ''Viola'' (plant), a genus of flowering plants Places United States * Vi ...
and
cyan Cyan () is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK c ...
on the
visible spectrum The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optica ...
. Hues of blue include indigo and
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
, closer to violet; pure blue, without any mixture of other colours; Azure, which is a lighter shade of blue, similar to the colour of the sky; Cyan, which is midway in the spectrum between blue and
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...
, and the other blue-greens such as
turquoise Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminium, with the chemical formula . It is rare and valuable in finer grades and has been prized as a gemstone for millennia due to its hue. The robi ...
,
teal alt=American teal duck (male), Green-winged teal (male) Teal is a greenish-blue color. Its name comes from that of a bird—the Eurasian teal (''Anas crecca'')—which presents a similarly colored stripe on its head. The word is often used ...
, and aquamarine. Blue also varies in shade or tint; darker shades of blue contain black or grey, while lighter tints contain white. Darker shades of blue include ultramarine,
cobalt blue Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminium(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Cobalt blue is lighte ...
,
navy blue Navy blue is a dark shade of the color blue. Navy blue got its name from the dark blue (contrasted with naval white) worn by officers in the Royal Navy since 1748 and subsequently adopted by other navies around the world. When this color name, ...
, and
Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
; while lighter tints include
sky blue Sky blue refers to a collection of shades comparable to that of a clear daytime sky. Typically it is a shade of cyan or light teal, though some iterations are closer to light Azure (color), azure or light blue. The term (as "sky blew") is atte ...
, azure, and
Egyptian blue Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pig ...
(for a more complete list see the
List of colours These are the lists of colors; * List of colors: A–F * List of colors: G–M * List of colors: N–Z * List of colors (alphabetical) * List of colors by shade * List of color palettes * List of Crayola crayon colors * List of RAL colours * Lis ...
).


As a structural colour

In nature, many blue phenomena arise from structural colouration, the result of interference between reflections from two or more surfaces of
thin films A thin film is a layer of materials ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...
, combined with refraction as light enters and exits such films. The geometry then determines that at certain angles, the light reflected from both surfaces interferes constructively, while at other angles, the light interferes destructively. Diverse colours therefore appear despite the absence of colourants.


Colourants

File:Egyptian blue.jpg,
Egyptian blue Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pig ...
File:Cobalt Blue.JPG,
Cobalt blue Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminium(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Cobalt blue is lighte ...
File:Bleu phtalo.jpg, Copper phthalocyanine File:YInMn_Blue_-_cropped.jpg,
YInMn blue YInMn Blue (/jɪnmɪn/; for the chemical symbols Y for yttrium, In for indium, and Mn for manganese), also known as Oregon Blue or Mas Blue, is an inorganic blue pigment that was discovered by Mas Subramanian and his (then) graduate student, ...
File:Prussian blue.jpg,
Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
, Fe CN)">Cyanide.html" ;"title="e(Cyanide">CN) is the blue of blueprint">Cyanide">CN<_a>).html" ;"title="Cyanide.html" ;"title="e(Cyanide">CN)">Cyanide.html" ;"title="e(Cyanide">CN) is the blue of blueprints.


Artificial blues

Egyptian blue Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pig ...
, the first artificial pigment, was produced in the third millennium BC in Ancient Egypt. It is produced by heating pulverized sand, copper, and natron. It was used in tomb paintings and funereal objects to protect the dead in their afterlife. Prior to the 1700s, blue colourants for artwork were mainly based on lapis lazuli and the related mineral ultramarine. A breakthrough occurred in 1709 when German druggist and pigment maker Johann Jacob Diesbach discovered
Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
. The new blue arose from experiments involving heating dried blood with iron sulphides and was initially called Berliner Blau. By 1710 it was being used by the French painter
Antoine Watteau Jean-Antoine Watteau (, , ; baptised 10 October 1684died 18 July 1721) Alsavailablevia Oxford Art Online (subscription needed). was a French Painting, painter and Drawing, draughtsman whose brief career spurred the revival of interest in colour ...
, and later his successor
Nicolas Lancret Nicolas Lancret (; 22 January 1690 – 14 September 1743) was a List of French artists, French painter. Born in Paris, he was a brilliant depicter of light comedy which reflected the tastes and manners of French society during the Régence, regen ...
. It became immensely popular for the manufacture of wallpaper, and in the 19th century was widely used by French impressionist painters. Beginning in the 1820s, Prussian blue was imported into Japan through the port of
Nagasaki , officially , is the capital and the largest Cities of Japan, city of Nagasaki Prefecture on the island of Kyushu in Japan. Founded by the Portuguese, the port of Portuguese_Nagasaki, Nagasaki became the sole Nanban trade, port used for tr ...
. It was called ''bero-ai'', or Berlin blue, and it became popular because it did not fade like traditional Japanese blue pigment, ''ai-gami'', made from the dayflower. Prussian blue was used by both
Hokusai , known mononymously as Hokusai, was a Japanese ukiyo-e artist of the Edo period, active as a painter and printmaker. His woodblock printing in Japan, woodblock print series ''Thirty-Six Views of Mount Fuji'' includes the iconic print ''The Gr ...
, in his wave paintings, and
Hiroshige or , born Andō Tokutarō (; 1797 – 12 October 1858), was a Japanese ''ukiyo-e'' artist, considered the last great master of that tradition. Hiroshige is best known for his horizontal-format landscape series '' The Fifty-three Stations ...
. In 1799 a French chemist,
Louis Jacques Thénard Louis Jacques Thénard (4 May 177721 June 1857) was a French chemist. Life He was born in a farm cottage near Nogent-sur-Seine in the Champagne district the son of a farm worker. In the post-Revolution French educational system, most boys rec ...
, made a synthetic cobalt blue pigment which became immensely popular with painters. In 1824 the Societé pour l'Encouragement d'Industrie in France offered a prize for the invention of an artificial
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
which could rival the natural colour made from lapis lazuli. The prize was won in 1826 by a chemist named Jean Baptiste Guimet, but he refused to reveal the formula of his colour. In 1828, another scientist, Christian Gmelin then a professor of chemistry in Tübingen, found the process and published his formula. This was the beginning of new industry to manufacture artificial ultramarine, which eventually almost completely replaced the natural product. In 1878 German chemists synthesized
indigo InterGlobe Aviation Limited (d/b/a IndiGo), is an India, Indian airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 64.1% domestic market ...
. This product rapidly replaced natural indigo, wiping out vast farms growing indigo. It is now the blue of blue jeans. As the pace of
organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...
accelerated, a succession of synthetic blue dyes were discovered including Indanthrone blue, which had even greater resistance to fading during washing or in the sun, and copper phthalocyanine. File:The Blue Boy.jpg, '' The Blue Boy'' (1770), featuring lapis lazuli, indigo, and cobalt colourants, File:Great Wave off Kanagawa2.jpg, ''
The Great Wave off Kanagawa is a woodblock print by Japanese ''ukiyo-e'' artist Hokusai, created in late 1831 during the Edo period of Japanese history. The print depicts three boats moving through a storm-tossed sea, with a large, cresting wave forming a spiral in t ...
'' illustrates the use of
Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
File:Indigoproduktion BASF 1890.JPG, A synthetic indigo dye factory in Germany in 1890.


Dyes for textiles and food

Woad ''Isatis tinctoria'', also called woad (), dyer's woad, dyer's-weed, or glastum, is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, ''Isati ...
and true indigo were once used but since the early 1900s, all indigo is synthetic. Produced on an industrial scale, indigo is the blue of blue jeans. Blue dyes are organic compounds, both synthetic and natural. For food, the triarylmethane dye Brilliant blue FCF is used for candies. The search continues for stable, natural blue dyes suitable for the food industry. Various
raspberry The raspberry is the edible fruit of several plant species in the genus ''Rubus'' of the Rosaceae, rose family, most of which are in the subgenus ''Rubus#Modern classification, Idaeobatus''. The name also applies to these plants themselves. Ras ...
-flavoured foods are dyed blue. This was done to distinguish
strawberry The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown Hybrid (biology), hybrid plant cultivated worldwide for its fruit. The genus ''Fragaria'', the strawberries, is in the rose family, Rosaceae. The fruit ...
,
watermelon The watermelon (''Citrullus lanatus'') is a species of flowering plant in the family Cucurbitaceae, that has a large, edible fruit. It is a Glossary of botanical terms#scandent, scrambling and trailing vine-like plant, and is plant breeding ...
and
raspberry The raspberry is the edible fruit of several plant species in the genus ''Rubus'' of the Rosaceae, rose family, most of which are in the subgenus ''Rubus#Modern classification, Idaeobatus''. The name also applies to these plants themselves. Ras ...
-flavoured foods. The company ICEE used Blue No. 1 for their blue raspberry ICEEs. File:Blue Raspberry Frozen Yogurt with White Chocolate Chips, Coconut, and Cherries.jpg, Blue Raspberry Frozen Yogurt with White Chocolate Chips, Coconut, and Cherries. File:Blue haribo jelly beans.jpg, Blue haribo jelly beans. Raspberry flavour. Bought in the UK. File:2019-11-09 19 29 30 A blue raspberry-flavored Jolly Rancher Hard Candy Stix after being unwrapped in the Dulles section of Sterling, Loudoun County, Virginia.jpg, A blue raspberry-flavoured Jolly Rancher Hard Candy Stix after being unwrapped in the Dulles section of Sterling, Loudoun County, Virginia. File:Indigo skeletal.svg, Chemical structure of
indigo dye Indigo dye is an organic compound with a distinctive indigo, blue color. Indigo is a natural dye obtained from the leaves of some plants of the Indigofera#Uses, ''Indigofera'' genus, in particular ''Indigofera tinctoria''. Dye-bearing ''Indigofer ...
, a widely produced blue dye. Blue jeans consist of 1–3% by weight of this
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
. File:C.I. Acid Blue 9.svg, upright=1.15, Chemical structure of C.I. Acid Blue 9, a dye commonly used in candies.


Pigments for painting and glass

Blue
pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...
s were once produced from minerals, especially
lapis lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, ''lāžward'', lapis lazuli is ...
and its close relative
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
. These minerals were crushed, ground into powder, and then mixed with a quick-drying binding agent, such as egg yolk ( tempera painting); or with a slow-drying oil, such as
linseed oil Linseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colorless to yellowish oil obtained from the dried, ripened seeds of the flax plant (''Linum usitatissimum''). The oil is obtained by pressing, sometimes followed by ...
, for
oil painting Oil painting is a painting method involving the procedure of painting with pigments combined with a drying oil as the Binder (material), binder. It has been the most common technique for artistic painting on canvas, wood panel, or oil on coppe ...
. Two inorganic but synthetic blue pigments are cerulean blue (primarily cobalt(II) stanate: ) and
Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
(milori blue: primarily ). The chromophore in blue
glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...
and glazes is
cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...
(II). Diverse cobalt(II) salts such as cobalt carbonate or cobalt(II) aluminate are mixed with the silica prior to firing. The cobalt occupies sites otherwise filled with silicon.


Inks

Methyl blue is the dominant blue pigment in inks used in pens.
Blueprint A blueprint is a reproduction of a technical drawing or engineering drawing using a contact print process on light-sensitive sheets introduced by Sir John Herschel in 1842. The process allowed rapid and accurate production of an unlimited number ...
ing involves the production of
Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
in situ.


Inorganic compounds

Certain metal
ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
s characteristically form blue solutions or blue salts. Of some practical importance,
cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...
is used to make the deep blue glazes and glasses. It substitutes for
silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
or
aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
ions in these materials. Cobalt is the blue
chromophore A chromophore is the part of a molecule responsible for its color. The word is derived . The color that is seen by our eyes is that of the light not Absorption (electromagnetic radiation), absorbed by the reflecting object within a certain wavele ...
in stained glass windows, such as those in
Gothic cathedrals Gothic cathedrals and churches are religious buildings constructed in Europe in Gothic style between the mid-12th century and the beginning of the 16th century. The cathedrals are notable particularly for their great height and their extensive u ...
and in Chinese
porcelain Porcelain (), also called china, is a ceramic material made by heating Industrial mineral, raw materials, generally including kaolinite, in a kiln to temperatures between . The greater strength and translucence of porcelain, relative to oth ...
beginning in the
Tang dynasty The Tang dynasty (, ; zh, c=唐朝), or the Tang Empire, was an Dynasties of China, imperial dynasty of China that ruled from 618 to 907, with an Wu Zhou, interregnum between 690 and 705. It was preceded by the Sui dynasty and followed ...
. Copper(II) (Cu2+) also produces many blue compounds, including the commercial
algicide Algaecide or algicide is a biocide used for killing and preventing the growth of algae, often defined in a loose sense that, beyond the biological definition, also includes cyanobacteria ("blue-green algae"). An algaecide may be used for controlled ...
copper(II) sulfate Copper(II) sulfate is an inorganic compound with the chemical formula . It forms hydrates , where ''n'' can range from 1 to 7. The pentahydrate (''n'' = 5), a bright blue crystal, is the most commonly encountered hydrate of copper(II) sulfate, whi ...
(CuSO4.5H2O). Similarly, vanadyl salts and solutions are often blue, e.g. vanadyl sulfate.


In nature


Sky and sea

When sunlight passes through the atmosphere, the blue wavelengths are scattered more widely by the oxygen and nitrogen molecules, and more blue comes to our eyes. This effect is called
Rayleigh scattering Rayleigh scattering ( ) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scat ...
, after
Lord Rayleigh John William Strutt, 3rd Baron Rayleigh ( ; 12 November 1842 – 30 June 1919), was an English physicist who received the Nobel Prize in Physics in 1904 "for his investigations of the densities of the most important gases and for his discovery ...
and confirmed by
Albert Einstein Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
in 1911. The sea is seen as blue for largely the same reason: the water absorbs the longer wavelengths of red and reflects and scatters the blue, which comes to the eye of the viewer. The deeper the observer goes, the darker the blue becomes. In the open sea, only about 1% of light penetrates to a depth of 200 metres (see
underwater An underwater environment is a environment of, and immersed in, liquid water in a natural or artificial feature (called a Water, body of water), such as an ocean, sea, lake, pond, reservoir, river, canal, or aquifer. Some characteristics of the ...
and euphotic depth). The colour of the sea is also affected by the colour of the sky, reflected by particles in the water; and by
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
and plant life in the water, which can make it look green; or by sediment, which can make it look brown. The farther away an object is, the more blue it often appears to the eye. For example, mountains in the distance often appear blue. This is the effect of atmospheric perspective; the farther an object is away from the viewer, the less contrast there is between the object and its background colour, which is usually blue. In a painting where different parts of the composition are blue, green and red, the blue will appear to be more distant, and the red closer to the viewer. The cooler a colour is, the more distant it seems. Blue light is scattered more than other wavelengths by the gases in the
atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
, hence our "blue planet". File:Top of Atmosphere.jpg, Earth's blue
halo HALO, halo, halos or haloes may refer to: Most common meanings * Halo (optical phenomenon) * Halo (religious iconography), a ring of light around the image of a head * ''Halo'' (franchise), a sci-fi video game series (2001–2021) Arts and en ...
when seen from space File:Aerial perspective 1.JPG, Another example of
Rayleigh scattering Rayleigh scattering ( ) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scat ...
File:LightningVolt Deep Blue Sea.jpg, The sea


Minerals

Lapis-lazuli hg.jpg,
Lapis-lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, ''lāžward'', lapis lazuli is a ...
Azurite - New Nevada Lode, La Sal, Utah, USA.jpg,
Azurite Azurite or '' Azure spar'Krivovichev V. G.'' Mineralogical glossary. Scientific editor A. G. Bulakh. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. ''(in Russian)'' is a soft, deep-blue copp ...
Natural ultramarine pigment.jpg, Natural
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
pigment Logan Sapphire SI.jpg,
Logan sapphire The Logan Sapphire is a sapphire from Sri Lanka. One of the largest blue faceted sapphires in the world, it was owned by Victor Sassoon and then purchased by M. Robert Guggenheim as a gift for his wife, Rebecca Pollard Guggenheim, who donated ...
 Some of the most desirable gems are blue, including
sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name ''sapphire ...
and tanzanite. Compounds of copper(II) are characteristically blue and so are many copper-containing minerals.
Azurite Azurite or '' Azure spar'Krivovichev V. G.'' Mineralogical glossary. Scientific editor A. G. Bulakh. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. ''(in Russian)'' is a soft, deep-blue copp ...
(, with a deep blue colour, was once employed in medieval years, but it is unstable pigment, losing its colour especially under dry conditions.
Lapis lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, ''lāžward'', lapis lazuli is ...
, mined in Afghanistan for more than three thousand years, was used for jewelry and ornaments, and later was crushed and powdered and used as a pigment. The more it was ground, the lighter the blue colour became. Natural
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
, made by grinding lapis lazuli into a fine powder, was the finest available blue pigment in the Middle Ages and the
Renaissance The Renaissance ( , ) is a Periodization, period of history and a European cultural movement covering the 15th and 16th centuries. It marked the transition from the Middle Ages to modernity and was characterized by an effort to revive and sur ...
. It was extremely expensive, and in
Italian Renaissance The Italian Renaissance ( ) was a period in History of Italy, Italian history between the 14th and 16th centuries. The period is known for the initial development of the broader Renaissance culture that spread across Western Europe and marked t ...
art, it was often reserved for the robes of the
Virgin Mary Mary was a first-century Jewish woman of Nazareth, the wife of Saint Joseph, Joseph and the mother of Jesus. She is an important figure of Christianity, venerated under titles of Mary, mother of Jesus, various titles such as Perpetual virginity ...
.


Plants and fungi

File:Blaue Primeln.JPG, ''Primula acaulis'' File:Ipomoea August 2007-1.jpg, Morning glory ('' Ipomoea acuminata'') File:Vaccinium corymbosum Beeren.jpg, ''
Vaccinium corymbosum ''Vaccinium corymbosum'', the northern highbush blueberry, is a North American species of blueberry. Other common names include blue huckleberry, tall huckleberry, swamp huckleberry, high blueberry, and swamp blueberry. Description ''Vaccinium ...
'' File:Vinca minor Nashville.jpg, ''
Vinca minor ''Vinca minor'' (common names lesser periwinkle or dwarf periwinkle) is a species of flowering plant in the dogbane family, native to central and southern Europe. Other vernacular names used in cultivation include small periwinkle, common peri ...
'' File:Delphinium denudatum 1.jpg, Blue Delphinium flower Lupinus-pilosus-2015-Zachi-Evenor-cropped02.jpg, Blue Lupme flower '' Lupinus pilosus'' File:Lactarius indigo 48568 edit.jpg, '' Lactarius indigo'' Intense efforts have focused on blue flowers and the possibility that natural blue colourants could be used as food dyes. Commonly, blue colours in plants are
anthocyanin Anthocyanins (), also called anthocyans, are solubility, water-soluble vacuole, vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart named a chemical compou ...
s: "the largest group of water-soluble pigments found widespread in the plant kingdom". In the few plants that exploit structural colouration, brilliant colours are produced by structures within cells. The most brilliant blue colouration known in any living tissue is found in the marble berries of '' Pollia condensata'', where a spiral structure of cellulose fibrils scattering blue light. The fruit of quandong (''Santalum acuminatum'') can appear blue owing to the same effect.


Animals

File:Morpho didius Male Dos MHNT.jpg, Morpho butterfly File:Indigo Bunting by Dan Pancamo 4.jpg,
Indigo bunting The indigo bunting (''Passerina cyanea'') is a small seed-eating bird in the cardinal family, Cardinalidae. It is bird migration, migratory, ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to ...
s have iridescent feathers. File:Mandrill-k-means.png, Blue facial ridges of
mandrill The mandrill (''Mandrillus sphinx'') is a large Old World monkey native to west central Africa. It is one of the most colorful mammals in the world, with red and blue skin on its face and posterior. The species is Sexual dimorphism, sexually ...
File:2009-03-29Dendrobates tinctorius azureus106.jpg,
Blue poison dart frog The blue poison dart frog or blue poison arrow frog (''Dendrobates tinctorius'' "azureus") is a poison dart frog found in the "forest islands" surrounded by the Sipaliwini Savanna in southern Suriname. Its indigenous Tiriyó language, Tiriyo na ...
File:Synchiropus splendidus 2 Luc Viatour cropped.png, The mandarin fish is one of few animal species with blue pigment Blue-pigmented animals are relatively rare. Examples of which include butterflies of the genus '' Nessaea'', where blue is created by pterobilin. Other blue pigments of animal origin include phorcabilin, used by other butterflies in '' Graphium'' and ''
Papilio ''Papilio'' is a genus in the swallowtail butterfly family, Papilionidae, as well as the only representative of the tribe Papilionini. The word ''papilio'' is Latin for butterfly. It includes the common yellow swallowtail ('' Papilio machaon'') ...
'' (specifically '' P. phorcas'' and '' P. weiskei''), and sarpedobilin, which is used by ''
Graphium sarpedon ''Graphium sarpedon'', the common bluebottle or blue triangle in Australia, is a species of Swallowtail butterfly, swallowtail butterfly that is found in East Asia, East, South Asia, South and Southeast Asia, as well as eastern Australia. There ...
''. Blue-pigmented
organelles In cell biology, an organelle is a specialized subunit, usually within a cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as organs are to the body, hence ''organelle,'' th ...
, known as "cyanosomes", exist in the
chromatophore Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopod A cephalopod is any member o ...
s of at least two fish species, the mandarin fish and the picturesque dragonet. More commonly, blueness in animals is a structural colouration; an optical interference effect induced by organized nanometre-sized scales or fibres. Examples include the plumage of several birds like the blue jay and
indigo bunting The indigo bunting (''Passerina cyanea'') is a small seed-eating bird in the cardinal family, Cardinalidae. It is bird migration, migratory, ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to ...
, the scales of butterflies like the morpho butterfly,
collagen Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a trip ...
fibres in the skin of some species of monkey and
opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North A ...
, and the iridophore cells in some fish and frogs.


Eyes

Blue eyes do not actually contain any blue pigment.
Eye colour Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. In humans, the pigmentation of ...
is determined by two factors: the
pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...
ation of the eye's iris and the
scattering In physics, scattering is a wide range of physical processes where moving particles or radiation of some form, such as light or sound, are forced to deviate from a straight trajectory by localized non-uniformities (including particles and radiat ...
of light by the
turbid Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and wate ...
medium in the stroma of the iris. In humans, the pigmentation of the iris varies from light brown to black. The appearance of blue, green, and hazel eyes results from the Tyndall scattering of light in the stroma, an optical effect similar to what accounts for the blueness of the sky. The irises of the eyes of people with blue eyes contain less dark
melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...
than those of people with brown eyes, which means that they absorb less short-wavelength blue light, which is instead reflected out to the viewer. Eye colour also varies depending on the lighting conditions, especially for lighter-coloured eyes. Blue eyes are most common in Ireland, the
Baltic Sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by the countries of Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden, and the North European Plain, North and Central European Plain regions. It is the ...
area and
Northern Europe The northern region of Europe has several definitions. A restrictive definition may describe northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54th parallel north, 54°N, or may be based on other ge ...
, and are also found in Eastern, Central, and
Southern Europe Southern Europe is also known as Mediterranean Europe, as its geography is marked by the Mediterranean Sea. Definitions of southern Europe include some or all of these countries and regions: Albania, Andorra, Bosnia and Herzegovina, Bulgaria, C ...
. Blue eyes are also found in parts of
Western Asia West Asia (also called Western Asia or Southwest Asia) is the westernmost region of Asia. As defined by most academics, UN bodies and other institutions, the subregion consists of Anatolia, the Arabian Peninsula, Iran, Mesopotamia, the Armenian ...
, most notably in
Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan, is a landlocked country located at the crossroads of Central Asia and South Asia. It is bordered by Pakistan to the Durand Line, east and south, Iran to the Afghanistan–Iran borde ...
,
Syria Syria, officially the Syrian Arab Republic, is a country in West Asia located in the Eastern Mediterranean and the Levant. It borders the Mediterranean Sea to the west, Turkey to Syria–Turkey border, the north, Iraq to Iraq–Syria border, t ...
,
Iraq Iraq, officially the Republic of Iraq, is a country in West Asia. It is bordered by Saudi Arabia to Iraq–Saudi Arabia border, the south, Turkey to Iraq–Turkey border, the north, Iran to Iran–Iraq border, the east, the Persian Gulf and ...
, and
Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...
. In
Estonia Estonia, officially the Republic of Estonia, is a country in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the Baltic Sea across from Sweden, to the south by Latvia, and to the east by Ru ...
, 99% of people have blue eyes. In
Denmark Denmark is a Nordic countries, Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark,, . also known as the Danish Realm, a constitutionally unitary state that includes the Autonomous a ...
in 1978, only 8% of the population had brown eyes, though through immigration, today that number is about 11%. In
Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
, about 75% have blue eyes. In the United States, as of 2006, 1 out of every 6 people, or 16.6% of the total population, and 22.3% of the white population, have blue eyes, compared with about half of Americans born in 1900, and a third of Americans born in 1950. Blue eyes are becoming less common among American children. In the US, males are 3–5% more likely to have blue eyes than females.


History


In the ancient world

File:Lapis bowl Iran, AO 26477.jpg,
Lapis lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, ''lāžward'', lapis lazuli is ...
bowl from Iran, end of 3rd – beginning of 2nd millennium BC (Louvre Museum) File:Tripodic goblet Louvre AO4079.jpg,
Egyptian blue Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pig ...
tripodic beaker imitating lapis lazuli. South Mesopotamia. (1399-1200 BC) File:WLA metmuseum Wall painting Polyphemus and Galaltea 4.jpg, Fresco of Polyphemus and Galatea, Pompei, using
Egyptian blue Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pig ...
(1st c. BC) (Metropolitan Museum) As early as the
7th millennium BC The 7th millennium BC spanned the years 7000 BC to 6001 BC (c. 9 ka to c. 8 ka). It is impossible to precisely date events around this millennium, and all dates mentioned here are estimates mostly based on geological and anthropologic ...
, lapis lazuli was mined in the
Sar-i Sang Sar-i Sang (or Sar-e Sang) (lit. "stone summit" in Persian) is a settlement in the Kuran Wa Munjan District of Badakhshan Province, Afghanistan, famous for its ancient lapis lazuli mines producing the world's finest lapis. It is located in the ...
mines,David Bomford and Ashok Roy, ''A Closer Look- Colour'' (2009), National Gallery Company, London, () in
Shortugai Shortugai (Shortughai), in Darqad District of northern Afghanistan, was a trading colony of the Indus Valley civilization (or Harappan Civilization) established around 2000 BC on the Oxus river (Amu Darya) near the lapis lazuli Lapis l ...
, and in other mines in
Badakhshan Badakhshan is a historical region comprising the Wakhan Corridor in northeast Afghanistan, eastern Tajikistan, and Taxkorgan Tajik Autonomous County in China. Badakhshan Province is one of the 34 provinces of Afghanistan. Much of historic ...
province in northeast
Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan, is a landlocked country located at the crossroads of Central Asia and South Asia. It is bordered by Pakistan to the Durand Line, east and south, Iran to the Afghanistan–Iran borde ...
. Lapis lazuli artifacts, dated to 7570 BC, have been found at
Bhirrana Bhirrana, also Bhirdana and Birhana, ( IAST: Bhirḍāna) is an archaeological site, located in a small village in the Fatehabad district of the north Indian state of Haryana. Bhirrana's earliest archaeological layers contained two charcoal sam ...
, which is the oldest site of
Indus Valley civilisation The Indus Valley Civilisation (IVC), also known as the Indus Civilisation, was a Bronze Age civilisation in the Northwestern South Asia, northwestern regions of South Asia, lasting from 3300 Common Era, BCE to 1300 BCE, and in i ...
. Lapis was highly valued by the Indus Valley Civilisation (7570–1900 BC). Lapis beads have been found at
Neolithic The Neolithic or New Stone Age (from Ancient Greek, Greek 'new' and 'stone') is an archaeological period, the final division of the Stone Age in Mesopotamia, Asia, Europe and Africa (c. 10,000 BCE to c. 2,000 BCE). It saw the Neolithic Revo ...
burials in
Mehrgarh Mehrgarh is a Neolithic archaeological site situated on the Kacchi Plain of Balochistan, Pakistan, Balochistan in Pakistan. It is located near the Bolan Pass, to the west of the Indus River and between the modern-day Pakistani cities of Quetta, ...
, the
Caucasus The Caucasus () or Caucasia (), is a region spanning Eastern Europe and Western Asia. It is situated between the Black Sea and the Caspian Sea, comprising parts of Southern Russia, Georgia, Armenia, and Azerbaijan. The Caucasus Mountains, i ...
, and as far away as
Mauritania Mauritania, officially the Islamic Republic of Mauritania, is a sovereign country in Maghreb, Northwest Africa. It is bordered by the Atlantic Ocean to the west, Western Sahara to Mauritania–Western Sahara border, the north and northwest, ...
. It was used in the funeral mask of Tutankhamun (1341–1323 BC). A term for Blue was relatively rare in many forms of ancient art and decoration, and even in ancient literature. The Ancient Greek poets described the sea as green, brown or "the colour of wine". The colour is mentioned several times in the
Hebrew Bible The Hebrew Bible or Tanakh (;"Tanach"
. '' tekhelet ''Tekhelet'' ( ''təḵēleṯ''; also transliterated ''tekheleth'', ''t'chelet'', ''techelet'', and ''techeiles'') is a highly valued blue dye that held great significance in history of the Mediterranean region, ancient Mediterranean civil ...
'. Reds, blacks, browns, and ochres are found in
cave painting In archaeology, cave paintings are a type of parietal art (which category also includes petroglyphs, or engravings), found on the wall or ceilings of caves. The term usually implies prehistoric art, prehistoric origin. These paintings were often c ...
s from the Upper
Paleolithic The Paleolithic or Palaeolithic ( years ago) ( ), also called the Old Stone Age (), is a period in human prehistory that is distinguished by the original development of stone tools, and which represents almost the entire period of human prehist ...
period, but not blue. Blue was also not used for dyeing fabric until long after red, ochre, pink, and purple. This is probably due to the perennial difficulty of making blue dyes and pigments. On the other hand, the rarity of blue pigment made it even more valuable. The earliest known blue dyes were made from plants –
woad ''Isatis tinctoria'', also called woad (), dyer's woad, dyer's-weed, or glastum, is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, ''Isati ...
in Europe,
indigo InterGlobe Aviation Limited (d/b/a IndiGo), is an India, Indian airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 64.1% domestic market ...
in Asia and Africa, while blue pigments were made from minerals, usually either
lapis lazuli Lapis lazuli (; ), or lapis for short, is a deep-blue metamorphic rock used as a semi-precious stone that has been prized since antiquity for its intense color. Originating from the Persian word for the gem, ''lāžward'', lapis lazuli is ...
or
azurite Azurite or '' Azure spar'Krivovichev V. G.'' Mineralogical glossary. Scientific editor A. G. Bulakh. — St.Petersburg: St.Petersburg Univ. Publ. House. 2009. — 556 p. — ISBN 978-5-288-04863-0. ''(in Russian)'' is a soft, deep-blue copp ...
, and required more. Blue glazes posed still another challenge since the early blue dyes and pigments were not thermally robust. In , the blue glaze
Egyptian blue Egyptian blue, also known as calcium copper silicate (CaCuSi4O10 or CaOCuO(SiO2)4 (calcium copper tetrasilicate)) or cuprorivaite, is a pigment that was used in ancient Egypt for thousands of years. It is considered to be the first synthetic pig ...
was introduced for ceramics, as well as many other objects.Chase, W.T. 1971, "Egyptian blue as a pigment and ceramic material." In: R. Brill (ed.) ''Science and Archaeology''. Cambridge, Mass: MIT Press. The Greeks imported indigo dye from India, calling it indikon, and they painted with Egyptian blue. Blue was not one of the four primary colours for Greek painting described by
Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...
(red, yellow, black, and white). For the Romans, blue was the colour of mourning, as well as the colour of barbarians. The Celts and Germans reportedly dyed their faces blue to frighten their enemies, and tinted their hair blue when they grew old. The Romans made extensive use of indigo and Egyptian blue pigment, as evidenced, in part, by frescos in
Pompeii Pompeii ( ; ) was a city in what is now the municipality of Pompei, near Naples, in the Campania region of Italy. Along with Herculaneum, Stabiae, and Villa Boscoreale, many surrounding villas, the city was buried under of volcanic ash and p ...
. The Romans had many words for varieties of blue, including , , , , , , , and , but two words, both of foreign origin, became the most enduring; , from the Germanic word ''blau'', which eventually became ''bleu'' or blue; and , from the Arabic word , which became azure. Blue was widely used in the decoration of churches in the Byzantine Empire. By contrast, in the Islamic world, blue was of secondary to green, believed to be the favourite colour of the
Prophet Mohammed Muhammad (8 June 632 CE) was an Arab religious and political leader and the founder of Islam. Muhammad in Islam, According to Islam, he was a prophet who was divinely inspired to preach and confirm the tawhid, monotheistic teachings of A ...
. At certain times in
Moorish Spain Al-Andalus () was the Muslim-ruled area of the Iberian Peninsula. The name refers to the different Muslim states that controlled these territories at various times between 711 and 1492. At its greatest geographical extent, it occupied most o ...
and other parts of the Islamic world, blue was the colour worn by Christians and Jews, because only Muslims were allowed to wear white and green.


In the Middle Ages

File:Vitraux Saint-Denis 190110 19.jpg, Stained glass window at
Saint Denis Basilica The Basilica of Saint-Denis (, now formally known as the ) is a large former medieval abbey church and present cathedral in the commune of Saint-Denis, a northern suburb of Paris. The building is of singular importance historically and archite ...
(1130–1140), coloured with
cobalt blue Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminium(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Cobalt blue is lighte ...
File:Vitrail Chartres Notre-Dame 210209 1.jpg, Detail of the Blue Virgin Window,
Chartres Cathedral Chartres Cathedral (, lit. Cathedral of Our Lady of Chartres) is a Catholic cathedral in Chartres, France, about southwest of Paris, and is the seat of the List of bishops of Chartres, Bishop of Chartres. Dedicated in honour of the Virgin Mary ( ...
(12th c.) File:Wilton diptych.jpg, The
Wilton Diptych The Wilton Diptych (made ) is a small portable diptych of two hinged panels, painted on both sides, now in the National Gallery, London. It is an extremely rare survival of a late medieval religious panel painting from England. The diptych was p ...
(1395–1399). The
Virgin Mary Mary was a first-century Jewish woman of Nazareth, the wife of Saint Joseph, Joseph and the mother of Jesus. She is an important figure of Christianity, venerated under titles of Mary, mother of Jesus, various titles such as Perpetual virginity ...
was traditionally shown in blue(14th c.) In the art and life of Europe during the early
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
, blue played a minor role. This changed dramatically between 1130 and 1140 in Paris, when the Abbe Suger rebuilt the
Saint Denis Basilica The Basilica of Saint-Denis (, now formally known as the ) is a large former medieval abbey church and present cathedral in the commune of Saint-Denis, a northern suburb of Paris. The building is of singular importance historically and archite ...
. Suger considered that light was the visible manifestation of the Holy Spirit. He installed
stained glass Stained glass refers to coloured glass as a material or art and architectural works created from it. Although it is traditionally made in flat panels and used as windows, the creations of modern stained glass artists also include three-dimensio ...
windows coloured with
cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...
, which, combined with the light from the red glass, filled the church with a bluish violet light. The church became the marvel of the
Christian world The terms Christendom or Christian world commonly refer to the global Christian community, Christian states, Christian-majority countries or countries in which Christianity is dominant or prevails.SeMerriam-Webster.com : dictionary, "Christen ...
, and the colour became known as the . In the years that followed even more elegant blue stained glass windows were installed in other churches, including at
Chartres Cathedral Chartres Cathedral (, lit. Cathedral of Our Lady of Chartres) is a Catholic cathedral in Chartres, France, about southwest of Paris, and is the seat of the List of bishops of Chartres, Bishop of Chartres. Dedicated in honour of the Virgin Mary ( ...
and
Sainte-Chapelle The Sainte-Chapelle (; ) is a royal chapel in the Gothic style, within the medieval Palais de la Cité, the residence of the Kings of France until the 14th century, on the Île de la Cité in the River Seine in Paris, France. Construction b ...
in Paris. In the 12th century the Roman Catholic Church dictated that painters in Italy (and the rest of Europe consequently) to paint the Virgin Mary with blue, which became associated with holiness, humility and virtue. In medieval paintings, blue was used to attract the attention of the viewer to the Virgin Mary. Paintings of the mythical
King Arthur According to legends, King Arthur (; ; ; ) was a king of Great Britain, Britain. He is a folk hero and a central figure in the medieval literary tradition known as the Matter of Britain. In Wales, Welsh sources, Arthur is portrayed as a le ...
began to show him dressed in blue. The coat of arms of the kings of France became an azure or light blue shield, sprinkled with golden
fleur-de-lis The ''fleur-de-lis'', also spelled ''fleur-de-lys'' (plural ''fleurs-de-lis'' or ''fleurs-de-lys''), is a common heraldic charge in the (stylized) shape of a lily (in French, and mean and respectively). Most notably, the ''fleur-de-lis'' ...
or lilies. Blue had come from obscurity to become the royal colour.


Renaissance through 18th century

Blue came into wider use beginning in the Renaissance, when artists began to paint the world with perspective, depth, shadows, and light from a single source. In Renaissance paintings, artists tried to create harmonies between blue and red, lightening the blue with lead white paint and adding shadows and highlights.
Raphael Raffaello Sanzio da Urbino (; March 28 or April 6, 1483April 6, 1520), now generally known in English as Raphael ( , ), was an Italian painter and architect of the High Renaissance. List of paintings by Raphael, His work is admired for its cl ...
was a master of this technique, carefully balancing the reds and the blues so no one colour dominated the picture.
Ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
was the most prestigious blue of the Renaissance, being more expensive than gold. Wealthy art patrons commissioned works with the most expensive blues possible. In 1616 Richard Sackville commissioned a portrait of himself by Isaac Oliver with three different blues, including ultramarine pigment for his stockings. File:Oliver Richard Sackville Earl of Dorset 1616.jpg, Portrait of Richard Sackville (1616), using three expensive blues, including ultramarine for his stockings File:MET DP251168.jpg,
Ming dynasty The Ming dynasty, officially the Great Ming, was an Dynasties of China, imperial dynasty of China that ruled from 1368 to 1644, following the collapse of the Mongol Empire, Mongol-led Yuan dynasty. The Ming was the last imperial dynasty of ...
, Porcelain vase painted with cobalt blue under transparent glaze. (15th c.) (Metropolitan Museum) File:Delftware plaque with New Testament scene 002.jpg,
Delftware Delftware or Delft pottery, also known as Delft Blue () or as delf, is a general term now used for Dutch tin-glazed earthenware, a form of faience. Most of it is blue and white pottery, and the city of Delft in the Netherlands was the major cen ...
plaque with cobalt blue painting (1683) (Rijksmuseum, Amsterdam) File:Portrait of Louis XIV of France in Coronation Robes (by Hyacinthe Rigaud) - Louvre Museum.jpg, Portrait of King
Louis XIV of France LouisXIV (Louis-Dieudonné; 5 September 16381 September 1715), also known as Louis the Great () or the Sun King (), was King of France from 1643 until his death in 1715. His verified reign of 72 years and 110 days is the List of longest-reign ...
in coronation robes, by
Hyacinthe Rigaud Jacint Rigau-Ros i Serra (; 18 July 1659 – 29 December 1743), known in French as Hyacinthe Rigaud (), was a Catalan-French baroque painter most famous for his portraits of Louis XIV and other members of the French nobility. Biography Rigau ...
(c. 1700) (Louvre Museum) File:Urn with cover MET DP104608.jpg, Urn by
Josiah Wedgwood Josiah Wedgwood (12 July 1730 – 3 January 1795) was an English potter, entrepreneur and abolitionist. Founding the Wedgwood company in 1759, he developed improved pottery bodies by systematic experimentation, and was the leader in the indu ...
(1780s) (Metropolitan Museum) File:Queen Maria I of Portugal (1734-1816) in an 18th century painting.jpg, Queen
Maria I of Portugal '' Dona'' Maria I (Maria Francisca Isabel Josefa Antónia Gertrudes Rita Joana; 17 December 1734 – 20 March 1816) also known as Maria the Pious in Portugal and Maria the Mad in Brazil, was Queen of Portugal from 24 February 1777 until her de ...
(late 1700s) File:Johannes Vermeer - Girl with a Pearl Earring - WGA24666.jpg, ''
Girl with a Pearl Earring ''Girl with a Pearl Earring'' () is an oil painting by Dutch Golden Age painter Johannes Vermeer, dated 1665. Going by various names over the centuries, it became known by its present title towards the end of the 20th century because of the e ...
'' by
Johannes Vermeer Johannes Vermeer ( , ; see below; also known as Jan Vermeer; October 1632 – 15 December 1675) was a Dutch painter who specialized in domestic interior scenes of middle-class life. He is considered one of the greatest painters of the Dutch ...
features
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
pigment An industry for the manufacture of fine blue and white pottery began in the 14th century in
Jingdezhen Jingdezhen is a prefecture-level city in eastern Jiangxi province with a total population of 1,669,057 (2018), bordering Anhui to the north. It is known as the "Porcelain Capital" because it has been producing Chinese ceramics for at least 1,0 ...
, China, using white Chinese porcelain decorated with patterns of
cobalt blue Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminium(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Cobalt blue is lighte ...
, imported from Persia. It was first made for the family of the Emperor of China, then was exported around the world, with designs for export adapted to European subjects and tastes. The Chinese blue style was also adapted by Dutch craftsmen in
Delft Delft () is a List of cities in the Netherlands by province, city and Municipalities of the Netherlands, municipality in the Provinces of the Netherlands, province of South Holland, Netherlands. It is located between Rotterdam, to the southeast, ...
and English craftsmen in
Staffordshire Staffordshire (; postal abbreviation ''Staffs''.) is a Ceremonial counties of England, ceremonial county in the West Midlands (region), West Midlands of England. It borders Cheshire to the north-west, Derbyshire and Leicestershire to the east, ...
in the 17th-18th centuries. in the 18th century, blue and white porcelains were produced by
Josiah Wedgwood Josiah Wedgwood (12 July 1730 – 3 January 1795) was an English potter, entrepreneur and abolitionist. Founding the Wedgwood company in 1759, he developed improved pottery bodies by systematic experimentation, and was the leader in the indu ...
and other British craftsmen.


19th-20th century

File:BrummellDighton1805.jpg,
Beau Brummel George Bryan "Beau" Brummell (7 June 1778 – 30 March 1840) was an important figure in Regency England, and for many years he was the arbiter of British men's fashion. At one time, he was a close friend of the Prince Regent, the future King ...
(1776–1840) introduced the ancestor of the modern blue suit File:D. Maria II (1834) - Joaquim Rafael (Museu Militar de Lisboa).png, Queen
Maria II of Portugal Dona Maria II (Maria da Glória Joana Carlota Leopoldina da Cruz Francisca Xavier de Paula Isidora Micaela Gabriela Rafaela Gonzaga de Habsburgo-Lorena e Bragança; 4 April 1819 – 15 November 1853) also known as "the Educator" () or as ...
in a blue and gold embroidered gown (1835) File:A Miner in His Cabin.jpg, A California gold miner in blue jeans (1853) File:Ferdinand Krumholz Isabel do Brasil 1853.jpg,
Isabel, Princess Imperial of Brazil '' Dona'' Isabel (29 July 1846 – 14 November 1921), called "the Redemptress", was the Princess Imperial ( heiress presumptive to the throne) of the Empire of Brazil and the Empire's regent on three occasions. Born in Rio de Janeiro as th ...
in light blue gown (1853) File:New York Metropolitan Police Uniforms 1871.jpg, New York City police in 1871 The early 19th century saw the ancestor of the modern blue business suit, created by
Beau Brummel George Bryan "Beau" Brummell (7 June 1778 – 30 March 1840) was an important figure in Regency England, and for many years he was the arbiter of British men's fashion. At one time, he was a close friend of the Prince Regent, the future King ...
(1776–1840), who set fashion at the London Court. It also saw the invention of blue jeans, a highly popular form of workers's costume, invented in 1853 by Jacob W. Davis who used metal rivets to strengthen blue
denim Denim is a sturdy cotton warp-faced textile in which the weft passes under two or more Warp (weaving), warp threads. This twill weave produces a diagonal ribbing that distinguishes it from cotton duck. Denim, as it is recognized today, was f ...
work clothing in the California gold fields. The invention was funded by San Francisco entrepreneur
Levi Strauss Levi Strauss ( ; born Löb Strauß, ; February 26, 1829 – September 26, 1902) was a German-born American businessman who founded the first company to manufacture blue jeans. His firm of Levi Strauss & Co. (Levi's) began in 1853 in San Franci ...
, and spread around the world. . File:Starry Night Over the Rhone.jpg, Van Gogh's ''
Starry Night Over the Rhône ''Starry Night'' (September 1888, ), commonly known as ''Starry Night Over the Rhône'', is one of Vincent van Gogh's paintings of Arles at night. It was painted on the bank of the Rhône that was only a one or two-minute walk from the Yellow ...
'' (1888). Blue used to create a mood or atmosphere. A cobalt blue sky, and cobalt or ultramarine water. File:Matisse Conversation.jpg, ''
The Conversation ''The Conversation'' is a 1974 American neo-noir mystery thriller film written, produced, and directed by Francis Ford Coppola. It stars Gene Hackman as a surveillance expert who faces a moral dilemma when his recordings reveal a potential ...
'' by
Henri Matisse Henri Émile Benoît Matisse (; 31 December 1869 – 3 November 1954) was a French visual arts, visual artist, known for both his use of colour and his fluid and original draughtsmanship. He was a drawing, draughtsman, printmaking, printmaker, ...
(1908–1912) Recognizing the emotional power of blue, many artists made it the central element of paintings in the 19th and 20th centuries. They included
Pablo Picasso Pablo Diego José Francisco de Paula Juan Nepomuceno María de los Remedios Cipriano de la Santísima Trinidad Ruiz y Picasso (25 October 1881 – 8 April 1973) was a Spanish painter, sculptor, printmaker, Ceramic art, ceramicist, and Scenic ...
,
Pavel Kuznetsov Pavel Varfolomevich Kuznetsov (1878–1968) was a painter and graphic artist. Life and career He studied at Saratov at Bogolyubov Art School (1891–1896), then Moscow School of Painting, Sculpture and Architecture (1897–1904) and for a y ...
and the
Blue Rose A blue rose is a flower of the genus ''Rosa'' (family Rosaceae) that presents blue-to-violet pigmentation instead of the more common red, white, or yellow, through use of artificial means such as dyes. Blue roses are often used to symbolize myst ...
art group, and Kandinsky and
Der Blaue Reiter ''Der Blaue Reiter'' (''The Blue Rider'') was a group of artists and a designation by Wassily Kandinsky and Franz Marc for their exhibition and publication activities, in which both artists acted as sole editors in the almanac of the same name ...
(The Blue Rider) school.Wassily Kandinsky, M. T. Sadler (Translator) ''Concerning the Spiritual in Art''. Dover Publ. (Paperback). 80 pp. .
Henri Matisse Henri Émile Benoît Matisse (; 31 December 1869 – 3 November 1954) was a French visual arts, visual artist, known for both his use of colour and his fluid and original draughtsmanship. He was a drawing, draughtsman, printmaking, printmaker, ...
expressed deep emotions with blue, "A certain blue penetrates your soul." In the second half of the 20th century, painters of the
abstract expressionist Abstract expressionism in the United States emerged as a distinct art movement in the aftermath of World War II and gained mainstream acceptance in the 1950s, a shift from the American social realism of the 1930s influenced by the Great Depressi ...
movement use blues to inspire ideas and emotions. Painter
Mark Rothko Mark Rothko ( ; Markus Yakovlevich Rothkowitz until 1940; September 25, 1903February 25, 1970) was an American abstract art, abstract painter. He is best known for his color field paintings that depicted irregular and painterly rectangular reg ...
observed that colour was "only an instrument;" his interest was "in expressing human emotions tragedy, ecstasy, doom, and so on".


In society and culture


Uniforms

File:HoratioNelson1.jpg,
Navy blue Navy blue is a dark shade of the color blue. Navy blue got its name from the dark blue (contrasted with naval white) worn by officers in the Royal Navy since 1748 and subsequently adopted by other navies around the world. When this color name, ...
derives its name from the uniform of
Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...
officers File:TSA agents, ca. 2016.jpg,
Transportation Security Administration The Transportation Security Administration (TSA) is an agency of the United States Department of Homeland Security (DHS) that has authority over the security of transportation systems within and connecting to the United States. It was created ...
agents File:2010. Донецк. Карнавал на день города 010.jpg, Ukrainian police officer in Donetsk File:PM do Rio muda o comando de 25 UPPs.jpg, Officers of the Military Police of Rio de Janeiro State, Brazil In the 17th century. The Prince-Elector of Brandenburg,
Frederick William I of Prussia Frederick William I (; 14 August 1688 – 31 May 1740), known as the Soldier King (), was King in Prussia and Elector of Brandenburg from 1713 until his death in 1740, as well as Prince of Neuchâtel. Born in Berlin, he was raised by the Hugu ...
, chose
Prussian blue Prussian blue (also known as Berlin blue, Brandenburg blue, Parisian and Paris blue) is a dark blue pigment produced by oxidation of ferrous ferrocyanide salts. It has the chemical formula . It consists of cations, where iron is in the oxidat ...
as the new colour of Prussian military uniforms, because it was made with
Woad ''Isatis tinctoria'', also called woad (), dyer's woad, dyer's-weed, or glastum, is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, ''Isati ...
, a local crop, rather than
Indigo InterGlobe Aviation Limited (d/b/a IndiGo), is an India, Indian airline headquartered in Gurgaon, Haryana, India. It is the largest List of airlines of India, airline in India by passengers carried and fleet size, with a 64.1% domestic market ...
, which was produced by the colonies of Brandenburg's rival, England. It was worn by the German army until World War I, with the exception of the soldiers of Bavaria, who wore sky-blue. In 1748, the
Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...
adopted a dark shade of blue for the uniform of officers.Heller (2010) p.32 It was first known as marine blue, now known as
navy blue Navy blue is a dark shade of the color blue. Navy blue got its name from the dark blue (contrasted with naval white) worn by officers in the Royal Navy since 1748 and subsequently adopted by other navies around the world. When this color name, ...
. The militia organized by
George Washington George Washington (, 1799) was a Founding Fathers of the United States, Founding Father and the first president of the United States, serving from 1789 to 1797. As commander of the Continental Army, Washington led Patriot (American Revoluti ...
selected blue and buff, the colours of the British Whig Party. Blue continued to be the colour of the field uniform of the US Army until 1902, and is still the colour of the dress uniform. In the 19th century, police in the United Kingdom, including the Metropolitan Police and the
City of London Police The City of London Police is the territorial police force#United Kingdom, territorial police force responsible for law enforcement within the City of London, England, including the Middle Temple, Middle and Inner Temple, Inner Temples. The for ...
also adopted a navy blue uniform. Similar traditions were embraced in France and Austria. It was also adopted at about the same time for the uniforms of the officers of the
New York City Police Department The City of New York Police Department, also referred to as New York City Police Department (NYPD), is the primary law enforcement agency within New York City. Established on May 23, 1845, the NYPD is the largest, and one of the oldest, munic ...
.


Gender

Blue is used to represent
males Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilisation. A male organism cannot reproduce sexually without access to ...
. Beginning as a trend the mid-19th century and applying primarily to clothing, gendered associations with blue became more widespread from the 1950s. The colour became associated with males after
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
. File:ANAB767300Restroomsign.jpg, This restroom sign on an
All Nippon Airways (ANA) is a Japanese airline headquartered in Minato, Tokyo. ANA operates services to both domestic and international destinations and is Japan's largest airline, ahead of its main rival flag carrier Japan Airlines. the airline has approximate ...
Boeing 767-300 uses pink for the female gender and blue for the male gender. File:Gender Reveal Cake (28005690402).jpg, Cake using blue to represent the male sex. File:Fynn Esser 2013-11-18 21-47.jpg, Baby blue newborn male clothing


Religion

File:Sri Mariamman Temple Singapore 2 amk.jpg, In
Hinduism Hinduism () is an Hypernymy and hyponymy, umbrella term for a range of Indian religions, Indian List of religions and spiritual traditions#Indian religions, religious and spiritual traditions (Sampradaya, ''sampradaya''s) that are unified ...
,
Krishna Krishna (; Sanskrit language, Sanskrit: कृष्ण, ) is a major deity in Hinduism. He is worshipped as the eighth avatar of Vishnu and also as the Supreme God (Hinduism), Supreme God in his own right. He is the god of protection, c ...
is depicted with blue skin File:Reknown blue domes of the Church dedicated to St. Spirou in Firostefani, Santorini island (Thira), Greece.jpg, Blue domes of the Church dedicated to St. Spirou in Firostefani,
Santorini Santorini (, ), officially Thira (, ) or Thera, is a Greek island in the southern Aegean Sea, about southeast from the mainland. It is the largest island of a small, circular archipelago formed by the Santorini caldera. It is the southern ...
island (Thira), Greece. File:Mezquita Shah, Isfahán, Irán, 2016-09-20, DD 64.jpg, Persian blue in Shah mosque (16th c.) in
Isfahan Isfahan or Esfahan ( ) is a city in the Central District (Isfahan County), Central District of Isfahan County, Isfahan province, Iran. It is the capital of the province, the county, and the district. It is located south of Tehran. The city ...
, Iran * Blue in Judaism: In the
Torah The Torah ( , "Instruction", "Teaching" or "Law") is the compilation of the first five books of the Hebrew Bible, namely the books of Genesis, Exodus, Leviticus, Numbers and Deuteronomy. The Torah is also known as the Pentateuch () ...
, the
Israelites Israelites were a Hebrew language, Hebrew-speaking ethnoreligious group, consisting of tribes that lived in Canaan during the Iron Age. Modern scholarship describes the Israelites as emerging from indigenous Canaanites, Canaanite populations ...
were commanded to put fringes, ''
tzitzit ''Tzitzit'' ( ''ṣīṣīṯ'', ; plural ''ṣīṣiyyōṯ'', Ashkenazi Hebrew, Ashkenazi: '; and Samaritan Hebrew, Samaritan: ') are specially knotted ritual Fringe (trim), fringes, or tassels, worn in antiquity by Israelites and today by o ...
'', on the corners of their garments, and to weave within these fringes a "twisted thread of blue (''tekhelet'')". In ancient days, this blue thread was made from a dye extracted from a Mediterranean snail called the ''hilazon''.
Maimonides Moses ben Maimon (1138–1204), commonly known as Maimonides (, ) and also referred to by the Hebrew acronym Rambam (), was a Sephardic rabbi and Jewish philosophy, philosopher who became one of the most prolific and influential Torah schola ...
claimed that this blue was the colour of "the clear noonday sky";
Rashi Shlomo Yitzchaki (; ; ; 13 July 1105) was a French rabbi who authored comprehensive commentaries on the Talmud and Hebrew Bible. He is commonly known by the List of rabbis known by acronyms, Rabbinic acronym Rashi (). Born in Troyes, Rashi stud ...
, the colour of the evening sky. According to several rabbinic sages, blue is the colour of God's Glory. Staring at this colour aids in mediation, bringing us a glimpse of the "pavement of sapphire, like the very sky for purity", which is a likeness of the Throne of God. (The
Hebrew Hebrew (; ''ʿÎbrit'') is a Northwest Semitic languages, Northwest Semitic language within the Afroasiatic languages, Afroasiatic language family. A regional dialect of the Canaanite languages, it was natively spoken by the Israelites and ...
word for glory) Many items in the ''
Mishkan According to the Hebrew Bible, the tabernacle (), also known as the Tent of the Congregation (, also Tent of Meeting), was the portable earthly dwelling of God used by the Israelites from the Exodus until the conquest of Canaan. Moses was instru ...
'', the portable sanctuary in the wilderness, such as the '' menorah'', many of the vessels, and the
Ark of the Covenant The Ark of the Covenant, also known as the Ark of the Testimony or the Ark of God, was a religious storage chest and relic held to be the most sacred object by the Israelites. Religious tradition describes it as a wooden storage chest decorat ...
, were covered with blue cloth when transported from place to place. * Blue in Christianity: Blue is particularly associated with the Mary (mother of Jesus), Virgin Mary. This was the result of a decree of Pope Gregory I (540–601) who ordered that all religious paintings should tell a story which was clearly comprehensible to all viewers, and that figures should be easily recognizable, especially that of the figure of Mary. If she was alone in the image, her costume was usually painted with the finest blue,
ultramarine Ultramarine is a deep blue pigment which was originally made by grinding lapis lazuli into a powder. Its lengthy grinding and washing process makes the natural pigment quite valuable—roughly ten times more expensive than the stone it comes fr ...
. If she was with Christ, her costume was usually painted with a less expensive pigment, to avoid outshining him.Heller, "Psychologie de la Colour - Effets et Symboliques", (2009),p. 32 * Blue in
Hinduism Hinduism () is an Hypernymy and hyponymy, umbrella term for a range of Indian religions, Indian List of religions and spiritual traditions#Indian religions, religious and spiritual traditions (Sampradaya, ''sampradaya''s) that are unified ...
: Many of the gods are depicted as having blue-coloured skin, particularly those associated with Vishnu, who is said to be the preserver of the world, and thus intimately connected to water.
Krishna Krishna (; Sanskrit language, Sanskrit: कृष्ण, ) is a major deity in Hinduism. He is worshipped as the eighth avatar of Vishnu and also as the Supreme God (Hinduism), Supreme God in his own right. He is the god of protection, c ...
and Rama, Vishnu's avatars, are usually depicted with blue skin. Shiva, the destroyer deity, is also depicted in a light-blue hue, and is called ''Nilakanta (Hinduism), Nīlakaṇṭha'', or blue-throated, for having swallowed poison to save the universe during the Samudra Manthana, the churning of the ocean of milk. Blue is used to symbolically represent the fifth, and the throat, chakra (Vishuddha). * Blue in Sikhism: The Nihang, Akali Nihangs warriors wear all-blue attire. Guru Gobind Singh also has a Roan (horse), blue roan horse. The Sikh Rehat Maryada states that the Nishan Sahib hoisted outside every Gurdwara, Gurudwara should be yellow, xanthic (Basanti in Punjabi language, Punjabi) or greyish blue (modern day
navy blue Navy blue is a dark shade of the color blue. Navy blue got its name from the dark blue (contrasted with naval white) worn by officers in the Royal Navy since 1748 and subsequently adopted by other navies around the world. When this color name, ...
) (Surmaaee in Punjabi language, Punjabi) colour. *Blue in Paganism: Blue is associated with peace, truth, wisdom, protection, and patience. It helps with healing, psychic ability, harmony, and understanding.


Sports

File:Italy Team - Rome, 1965.jpg, The Italy national football team, Italian national football team File:Serbia national volleyball team at the 2012 Summer Olympics (7913882066).jpg, Serbian national volleyball team, 2012 Olympics File:Jack White, Duke Blue Devils.jpg, Basketball player for the Blue Devils at Cassell Coliseum In sports, blue is widely represented in uniforms in part because the majority of national teams wear the colours of their national flag. For example, the national men's football team of France national football team, France are known as ''Les Bleus'' (the Blues). Similarly, Argentina national football team, Argentina, Italy national football team, Italy, and Uruguay national football team, Uruguay wear blue shirts. The Asian Football Confederation and the Oceania Football Confederation use blue text on their logos. Blue is well represented in baseball (Toronto Blue Jays, Blue Jays), National Basketball Association, basketball, and National Football League, American football, and National Hockey League, Ice hockey. The India national cricket team, Indian national cricket team wears blue uniform during One day international matches, as such the team is also referred to as "Men in Blue".


Politics

File:Flag of the United Nations.svg, Flag of the
United Nations The United Nations (UN) is the Earth, global intergovernmental organization established by the signing of the Charter of the United Nations, UN Charter on 26 June 1945 with the stated purpose of maintaining international peace and internationa ...
, approximates "sky blue" File:Flag of Europe.svg, Flag of the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
is "reflex blue", a medium dark blue File:Red states and blue states of the US based on data from the 2008, 2012, 2016 and 2020 presidential elections.svg, A presidential-election map of the US, 2008–2020. States that consistently vote for Democrats are termed "blue states". Unlike red or green, blue was not strongly associated with any particular country, religion or political movement. As the colour of harmony, it was chosen as the colour for the flags of the
United Nations The United Nations (UN) is the Earth, global intergovernmental organization established by the signing of the Charter of the United Nations, UN Charter on 26 June 1945 with the stated purpose of maintaining international peace and internationa ...
, the
European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
, and NATO.Heller, "Psychologie de la Couleur" pp. 36-37 In politics, blue is often used as the colour of conservative parties, contrasting with the red associated with left-wing parties. Some conservative parties that use the colour blue include the Conservative Party (UK), Conservative Party of Canada, Liberal Party of Australia, Liberal Party (Brazil, 2006), Liberal Party of Brazil, and Likud of Israel. However, in some countries, blue is not associated main conservative party. In the United States, the liberal Democratic Party (United States), Democratic Party is associated with blue, while the conservative Republican Party (United States), Republican Party is associated with red. US states which have been won by the Democratic Party in four consecutive presidential elections are termed "blue states", while those that have been won by the Republican Party are termed "red states". South Korea also uses this colour model, with the Democratic Party (South Korea, 2015), Democratic Party on the left using blue and the People Power Party (South Korea), People Power Party on the right using red.


See also

* Engineer's blue * Lists of colours * Non-photo blue * Blue pigments


References


Works cited

* (page numbers refer to the French translation) * * * * * * *


Further reading

* * * *


External links

* *
"Friday essay: from the Great Wave to Starry Night, how a blue pigment changed the world", By Hugh Davies, theconversation.com
{{Authority control Blue symbols, Optical spectrum Primary colors Rainbow colors Secondary colors Shades of blue, Shades of violet Web colors Masculinity