color theory Color theory, or more specifically traditional color theory, is a historical body of knowledge describing the behavior of colors, namely in color mixing, color contrast effects, color harmony, color schemes and color symbolism. Modern color th ...

, 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 625–750 nanometres. It is a primary color in the RGB color model and a seconda ...

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 (: 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 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 spectral line with a single wavelength or frequency of light in the visible spectrum, or a relatively narrow spectral band (e.g. lasers). Every wave of visible ...

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, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

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'' originated as an acronym for light amplification by stimulated emission of radi ...

, 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 retina of the vertebrate eye. Cones are active in daylight conditions and enable photopic vision, as opposed to rod cells, which are active in dim light and enable scotopic vision. Most v ...

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 re ...

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

purple Purple is a color similar in appearance to violet light. In the RYB color model historically used in the arts, purple is a secondary color created by combining red and blue pigments. In the CMYK color model used in modern printing, purple is ...

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 is 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 d ...

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 classifica ...

for examples) that form the interior of a

triangle A triangle is a polygon with three corners and three sides, one of the basic shapes in geometry. The corners, also called ''vertices'', are zero-dimensional points while the sides connecting them, also called ''edges'', are one-dimension ...

between

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 ...

and the line of purples in the CIE chromaticity diagram.

In color spaces

In 3-dimensional

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 represe ...

s the line, if present, becomes a 2-dimensional shape. For example, in the CIE XYZ 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 an American limited liability company headquartered in Carlstadt, New Jersey, and best known for its Pantone Matching System (PMS), a proprietary color order system used in a variety of industries, notably gr ...

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 stand ...

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 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 ...

. The

RGB color model The RGB color model is an additive color, 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 ...

, 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-function see Sigma additivity * Additive category, a preadditive category with fin ...

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

sRGB sRGB (standard RGB) is a colorspace, for use on monitors, printers, and the World Wide Web. It was initially proposed by HP and Microsoft in 1996 and became an official standard of the International Electrotechnical Commission (IEC) as IEC 6 ...

(pictured) runs approximately parallel to the line, connecting the

primaries Primary elections or primaries are elections held to determine which candidates will run in an upcoming general election. In a partisan primary, a political party selects a candidate. Depending on the state and/or party, there may be an "open pri ...

red and (color wheel) blue, and thus purples near the line are absent from the

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 sRGB.

Magenta Magenta () is a purple-red color. On color wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) color models, it is located precisely midway between blue and red. It is one of the four colors of ink used in colo ...

ink, which is one of

CMYK The CMYK color model (also known as process color, or four color) is a subtractive color model, based on the CMY color model, used in color printing, and is also used to describe the printing process itself. The abbreviation ''CMYK'' refers ...

's primaries, is also very distant from the line for the reason explained above. The wide-gamut RGB color space 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 space Shades of violet Shades of magenta Shades of red line

In color spaces

Table of highly saturated purples

See also

Notes and references

External links