In color theory, the line of purples or purple boundary is the locus on the edge of the chromaticity diagram formed between extreme spectral

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 625–740 nanometres. It is a primary color in the RGB color model and a secondary ...

and violet. Except for these endpoints of the line, colors on the line are non-spectral (no monochromatic light source can generate them). Rather, every color on the line is a unique mixture in a ratio of fully saturated red and fully saturated violet, the two spectral color endpoints of visibility on the

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...

of pure hues. Colors on the line and

spectral color A spectral color is a color that is evoked by ''monochromatic light'', i.e. either a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths (e.g. lasers). Every wavelength of visible light is percei ...

s are the only ones that are fully saturated in the sense that, for any point on the line, no other possible color being a mixture of red and violet is more saturated than it. Unlike spectral colors, which may be implemented, for example, by the nearly monochromatic

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahe ...

of a

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" is an acronym for "light amplification by stimulated emission of radiation". The firs ...

, with precision much finer than human chromaticity resolution, colors on the line are more difficult to depict. The sensitivity of each type of human

cone cell Cone cells, or cones, are photoreceptor cells in the retinas of vertebrate eyes including the human eye. They respond differently to light of different wavelengths, and the combination of their responses is responsible for color vision. Cones ...

to ''both'' spectral red and spectral violet, being at the opposite endpoints of the line and at the extremes of the visible spectrum, is very low. (See

luminosity function A luminous efficiency function or luminosity function represents the average spectral sensitivity of human visual perception of light. It is based on subjective judgements of which of a pair of different-colored lights is brighter, to describe ...

.) Therefore, common purple colors are not highly bright. The line of purples, a theoretical boundary of chromaticity, is distinct from "

purple Purple is any of a variety of colors with hue between red and blue. In the RGB color model used in computer and television screens, purples are produced by mixing red and blue light. In the RYB color model historically used by painters, pu ...

s", a more general denomination of colors, which also refers to less than fully saturated colors (see

shades of purple There are numerous variations of the color purple, a sampling of which are shown below. In common English usage, ''purple'' is a range of hues of color occurring between red and blue. However, the meaning of the term purple is not well define ...

and

shades of pink Pink colors are usually light or desaturated shades of reds, roses, and magentas which are created on computer and television screens using the RGB color model and in printing with the CMYK color model. As such, it is an arbitrary classificati ...

for examples) that form the interior of a

triangle A triangle is a polygon with three edges and three vertices. It is one of the basic shapes in geometry. A triangle with vertices ''A'', ''B'', and ''C'' is denoted \triangle ABC. In Euclidean geometry, any three points, when non-collinear ...

between

white White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White o ...

and the line of purples in the

CIE chromaticity diagram The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that defin ...

In color spaces

3-dimensional Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position of an element (i.e., point). This is the informal ...

color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of colorwhether such representation entails an analog or a digital represen ...

s the line, if present, becomes a 2-dimensional shape. For example, in the

CIE XYZ The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that defin ...

it is a planar sector bounded by black–red and black–violet rays. In systems premised on pigment colors, such as the Munsell and

Pantone Pantone LLC (stylized as PANTONE) is a limited liability company headquartered in Carlstadt, New Jersey. The company is best known for its Pantone Matching System (PMS), a proprietary color space used in a variety of industries, notably graphi ...

systems, boundary purples might be absent because the maximally possible

lightness Lightness is a visual perception of the luminance (L) of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a stan ...

of a pigment vanishes when its chromaticity approaches the Line, such that purple pigments near the line are indistinguishable from

black Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white have of ...

. The

RGB color model The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three addit ...

, although ''theoretically'' capable of approximating the colors of the line because it is an

additive Additive may refer to: Mathematics * Additive function, a function in number theory * Additive map, a function that preserves the addition operation * Additive set-functionn see Sigma additivity * Additive category, a preadditive category with fi ...

system, usually practically fails because of the limitations of the light source used. The boundary of

sRGB sRGB is a standard RGB (red, green, blue) color space that HP and Microsoft created cooperatively in 1996 to use on monitors, printers, and the World Wide Web. It was subsequently standardized by the International Electrotechnical Commission ( ...

(pictured) runs approximately parallel to the line, connecting the primaries red and (color wheel) blue, and thus purples near the line are absent from the

gamut In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain ''complete subset'' of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circ ...

of sRGB.

Magenta Magenta () is a color that is variously defined as pinkish- purplish-red, reddish-purplish-pink or mauvish- crimson. On color wheels of the RGB (additive) and CMY (subtractive) color models, it is located exactly midway between red and blue. ...

ink, which is one of CMYK's primaries, is also very distant from the line for the reason explained above. The

wide-gamut RGB color space The wide-gamut RGB color space (or Adobe Wide Gamut RGB) is an RGB color space developed by Adobe Systems, that offers a large gamut by using pure spectral primary colors. It is able to store a wider range of color values than sRGB or Adobe ...

approximates the colors on the line better, but devices capable of displaying colors with this enhanced system are prohibitively expensive for ordinary consumers.

Table of highly saturated purples

Most of the names of the purple colors in the table below do not denominate colors on the line of purples, but instead are slightly less than maximally colorful, i.e. saturated. Approximations of colors outside sRGB.

Notes and references

*Kenneth L. Kosanke, B. J. Kosanke, ''The Illustrated Dictionary of Pyrotechnics'', p. 72 {{Reflist

External links

* HyperPhysics
"Color Perception"
*Spectra software and databases: https://web.archive.org/web/20110409161524/http://spectra.at.tut.by/en/page0.html Color

In color spaces

Table of highly saturated purples

See also

Notes and references

External links