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{{for2|other uses of "Color" and "Colour"|Color (disambiguation). {{nowrap|For editing Wikipedia, see (Help:Using colors)}}. {{nowrap|See also, Colorful (disambiguation) and Lists of colors}}}}{{pp-vandalism|small=yes}}{{short description|Characteristic of human visual perception}}{{more citations needed|date=September 2017}}File:64 365 Color Macro (5498808099).jpg|right|300px|thumb|Colored pencilColored pencilFile:Nasir-al molk -1.jpg|thumb|300px|Color effect – Sunlight shining through stained glass onto carpet (Nasir ol Molk Mosque located in Shiraz, IranIranFile:Colour shift.jpg|300px|thumb|Colors can appear different depending on their surrounding colors and shapes. The two small squares have exactly the same color, but the right one looks slightly darker, the Chubb illusionChubb illusionColor (American English), or colour (Commonwealth English), is the characteristic of human visual perception described through color categories, with names such as red, orange, yellow, green, blue, or purple. This perception of color derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. Color categories and physical specifications of color are associated with objects through the wavelength of the light that is reflected from them. This reflection is governed by the object's physical properties such as light absorption, emission spectra, etc.By defining a color space, colors can be identified numerically by coordinates, which in 1931 were also named in global agreement with internationally agreed color names like mentioned above (red, orange, etc.) by the International Commission on Illumination. The RGB color space for instance is a color space corresponding to human trichromacy and to the three cone cell types that respond to three bands of light: long wavelengths, peaking near 564–580 nm (red); medium-wavelength, peaking near 534–545 nm (green); and short-wavelength light, near 420–440 nm (blue).BOOK, Günther, Wyszecki, Stiles, W.S., 1982, Colour Science: Concepts and Methods, Quantitative Data and Formulae, 2nd, Wiley Series in Pure and Applied Optics, New York, 978-0-471-02106-3, BOOK, R.W.G. Hunt, 2004, The Reproduction of Colour, 6th, 11–12, Wiley–IS&T Series in Imaging Science and Technology, Chichester UK, 978-0-470-02425-6, There may also be more than three color dimensions in other color spaces, such as in the CMYK color model, wherein one of the dimensions relates to a color's colorfulness).The photo-receptivity of the "eyes" of other species also varies considerably from that of humans and so results in correspondingly different color perceptions that cannot readily be compared to one another. Honeybees and bumblebees for instance have trichromatic color vision sensitive to ultraviolet but is insensitive to red. Papilio butterflies possess six types of photoreceptors and may have pentachromatic vision.JOURNAL, Arikawa K, Spectral organization of the eye of a butterfly, Papilio, J. Comp. Physiol. A, 189, 11, 791–800, November 2003, 14520495, 10.1007/s00359-003-0454-7, The most complex color vision system in the animal kingdom has been found in stomatopods (such as the mantis shrimp) with up to 12 spectral receptor types thought to work as multiple dichromatic units.JOURNAL, Cronin TW, Marshall NJ, A retina with at least ten spectral types of photoreceptors in a mantis shrimp, Nature, 339, 137–40, 1989, 10.1038/339137a0, 6220, 1989Natur.339..137C, The science of color is sometimes called chromatics, colorimetry, or simply color science. It includes the study of the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range (that is, what is commonly referred to simply as light).{{TOC limit|3}}

Physics of color

File:Rendered Spectrum.png|thumb|400px|Continuous optical spectrum rendered into the sRGBsRGB{| class="wikitable" style="float:right; width:400px; margin:1em 0 1em 1em; clear:right;"The colors of the visible light spectrumFUNDAMENTALS OF ATMOSPHERIC RADIATION: AN INTRODUCTION WITH 400 PROBLEMS, Craig F. Bohren, Wiley-VCH, 2006, 978-3-527-40503-9,weblink 214,, !style="text-align: left" colspan="2" |Color! abbr="wavelength" | Wavelengthinterval! abbr="frequency" | Frequencyinterval
! style="background:#f00;"|!style="text-align: left"|Red| ~ 700–635 nm| ~ 430–480 THz
! style="background:#ff8000"|!style="text-align: left"|Orange| ~ 635–590 nm| ~ 480–510 THz
! style="background:#ff0"|!style="text-align: left"|Yellow| ~ 590–560 nm| ~ 510–540 THz
! style="background:#0f0"|!style="text-align: left"|Green| ~ 560–520 nm| ~ 540–580 THz
! style="background:#0ff"|!style="text-align: left"|Cyan| ~ 520–490 nm| ~ 580–610 THz
! style="background:#00f"|! style="text-align: left"|Blue| ~ 490–450 nm| ~ 610–670 THz
! style="background:#8000ff" |!style="text-align: left"|Violet| ~ 450–400 nm| ~ 670–750 THz
{| class="wikitable" style="float:right; width:400px; margin:hem 0 1em 1em; clear:right;"|+ Color, wavelength, frequency and energy of light!style="text-align: left"|Color!lambda ,!(nm)!nu ,!(THz)!nu_b ,!(μm−1)!E ,!(eV)!E ,!(kJ mol−1)
style="text-align:right;"!style="text-align: left"|Infrared| >1000| The trichromatic theory is strictly true when the visual system is in a fixed state of adaptation. In reality, the visual system is constantly adapting to changes in the environment and compares the various colors in a scene to reduce the effects of the illumination. If a scene is illuminated with one light, and then with another, as long as the difference between the light sources stays within a reasonable range, the colors in the scene appear relatively constant to us. This was studied by Edwin Land in the 1970s and led to his retinex theory of color constancy.Both phenomena are readily explained and mathematically modeled with modern theories of chromatic adaptation and color appearance (e.g. CIECAM02, iCAM).M.D. Fairchild, Color Appearance Models {{webarchive |url= |date=May 5, 2011 }}, 2nd Ed., Wiley, Chichester (2005). There is no need to dismiss the trichromatic theory of vision, but rather it can be enhanced with an understanding of how the visual system adapts to changes in the viewing environment.

Color naming

{{See also|Lists of colors|Web colors}}(File:1Mcolors.png|thumb|This picture contains one million pixels, each one a different color)Colors vary in several different ways, including hue (shades of red, orange, yellow, green, blue, and violet), saturation, brightness, and gloss. Some color words are derived from the name of an object of that color, such as "orange" or "salmon", while others are abstract, like "red".In the 1969 study (Basic Color Terms: Their Universality and Evolution), Brent Berlin and Paul Kay describe a pattern in naming "basic" colors (like "red" but not "red-orange" or "dark red" or "blood red", which are "shades" of red). All languages that have two "basic" color names distinguish dark/cool colors from bright/warm colors. The next colors to be distinguished are usually red and then yellow or green. All languages with six "basic" colors include black, white, red, green, blue, and yellow. The pattern holds up to a set of twelve: black, gray, white, pink, red, orange, yellow, green, blue, purple, brown, and azure (distinct from blue in Russian and Italian, but not English).


Individual colors have a variety of cultural associations such as national colors (in general described in individual color articles and color symbolism). The field of color psychology attempts to identify the effects of color on human emotion and activity. Chromotherapy is a form of alternative medicine attributed to various Eastern traditions. Colors have different associations in different countries and cultures.WEB,weblinkweblink dead, 2010-10-12, Chart: Color Meanings by Culture, 2010-06-29, Different colors have been demonstrated to have effects on cognition. For example, researchers at the University of Linz in Austria demonstrated that the color red significantly decreases cognitive functioning in men.JOURNAL, Gnambs, Timo, Appel, Markus, Batinic, Bernad, 2010, Color red in web-based knowledge testing, Computers in Human Behavior, 26, 6, 1625–31, 10.1016/j.chb.2010.06.010,

Spectral colors and color reproduction

File:CIExy1931 fixed.svg|right|thumb|upright|The CIE 1931 color spacechromaticity diagram. The outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers. The colors depicted depend on the color spacecolor spaceMost light sources are mixtures of various wavelengths of light. Many such sources can still effectively produce a spectral color, as the eye cannot distinguish them from single-wavelength sources. For example, most computer displays reproduce the spectral color orange as a combination of red and green light; it appears orange because the red and green are mixed in the right proportions to allow the eye's cones to respond the way they do to the spectral color orange.A useful concept in understanding the perceived color of a non-monochromatic light source is the dominant wavelength, which identifies the single wavelength of light that produces a sensation most similar to the light source. Dominant wavelength is roughly akin to hue.There are many color perceptions that by definition cannot be pure spectral colors due to desaturation or because they are purples (mixtures of red and violet light, from opposite ends of the spectrum). Some examples of necessarily non-spectral colors are the achromatic colors (black, gray, and white) and colors such as pink, tan, and magenta.Two different light spectra that have the same effect on the three color receptors in the human eye will be perceived as the same color. They are metamers of that color. This is exemplified by the white light emitted by fluorescent lamps, which typically has a spectrum of a few narrow bands, while daylight has a continuous spectrum. The human eye cannot tell the difference between such light spectra just by looking into the light source, although reflected colors from objects can look different. (This is often exploited; for example, to make fruit or tomatoes look more intensely red.)Similarly, most human color perceptions can be generated by a mixture of three colors called primaries. This is used to reproduce color scenes in photography, printing, television, and other media. There are a number of methods or color spaces for specifying a color in terms of three particular primary colors. Each method has its advantages and disadvantages depending on the particular application.No mixture of colors, however, can produce a response truly identical to that of a spectral color, although one can get close, especially for the longer wavelengths, where the CIE 1931 color space chromaticity diagram has a nearly straight edge. For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red color receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green.Because of this, and because the primaries in color printing systems generally are not pure themselves, the colors reproduced are never perfectly saturated spectral colors, and so spectral colors cannot be matched exactly. However, natural scenes rarely contain fully saturated colors, thus such scenes can usually be approximated well by these systems. The range of colors that can be reproduced with a given color reproduction system is called the gamut. The CIE chromaticity diagram can be used to describe the gamut.Another problem with color reproduction systems is connected with the acquisition devices, like cameras or scanners. The characteristics of the color sensors in the devices are often very far from the characteristics of the receptors in the human eye. In effect, acquisition of colors can be relatively poor if they have special, often very "jagged", spectra caused for example by unusual lighting of the photographed scene.A color reproduction system "tuned" to a human with normal color vision may give very inaccurate results for other observers.The different color response of different devices can be problematic if not properly managed. For color information stored and transferred in digital form, color management techniques, such as those based on ICC profiles, can help to avoid distortions of the reproduced colors. Color management does not circumvent the gamut limitations of particular output devices, but can assist in finding good mapping of input colors into the gamut that can be reproduced.

Additive coloring

(File:AdditiveColor.svg|thumb|Additive color mixing: combining red and green yields yellow; combining all three primary colors together yields white.)Additive color is light created by mixing together light of two or more different colors. Red, green, and blue are the additive primary colors normally used in additive color systems such as projectors and computer terminals.

Subtractive coloring

(File:SubtractiveColor.svg|thumb|Subtractive color mixing: combining yellow and magenta yields red; combining all three primary colors together yields black)Subtractive coloring uses dyes, inks, pigments, or filters to absorb some wavelengths of light and not others. The color that a surface displays comes from the parts of the visible spectrum that are not absorbed and therefore remain visible. Without pigments or dye, fabric fibers, paint base and paper are usually made of particles that scatter white light (all colors) well in all directions. When a pigment or ink is added, wavelengths are absorbed or "subtracted" from white light, so light of another color reaches the eye.If the light is not a pure white source (the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different color. Red paint, viewed under blue light, may appear black. Red paint is red because it scatters only the red components of the spectrum. If red paint is illuminated by blue light, it will be absorbed by the red paint, creating the appearance of a black object.

Structural color

{{further|Structural coloration|Animal coloration}}Structural colors are colors caused by interference effects rather than by pigments. Color effects are produced when a material is scored with fine parallel lines, formed of one or more parallel thin layers, or otherwise composed of microstructures on the scale of the color's wavelength. If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colors: the blue of the sky (Rayleigh scattering, caused by structures much smaller than the wavelength of light, in this case air molecules), the luster of opals, and the blue of human irises. If the microstructures are aligned in arrays, for example the array of pits in a CD, they behave as a diffraction grating: the grating reflects different wavelengths in different directions due to interference phenomena, separating mixed "white" light into light of different wavelengths. If the structure is one or more thin layers then it will reflect some wavelengths and transmit others, depending on the layers' thickness.Structural color is studied in the field of thin-film optics. The most ordered or the most changeable structural colors are iridescent. Structural color is responsible for the blues and greens of the feathers of many birds (the blue jay, for example), as well as certain butterfly wings and beetle shells. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle. Numerous scientists have carried out research in butterfly wings and beetle shells, including Isaac Newton and Robert Hooke. Since 1942, electron micrography has been used, advancing the development of products that exploit structural color, such as "photonic" cosmetics.WEB,weblink Economic and Social Research Council – Science in the Dock, Art in the Stocks, 2007-10-07, dead,weblink" title="">weblink November 2, 2007,

Additional terms

  • Color wheel: an illustrative organization of color hues in a circle that shows relationships.
  • Colorfulness, chroma, purity, or saturation: how "intense" or "concentrated" a color is. Technical definitions distinguish between colorfulness, chroma, and saturation as distinct perceptual attributes and include purity as a physical quantity. These terms, and others related to light and color are internationally agreed upon and published in the CIE Lighting Vocabulary.CIE Pub. 17-4, International Lighting Vocabulary {{webarchive|url= |date=2010-02-27 }}, 1987. WEB,weblink Archived copy, 2010-02-05, dead,weblink" title="">weblink 2010-02-27, More readily available texts on colorimetry also define and explain these terms.R.S. Berns, Principles of Color Technology {{webarchive|url= |date=2012-01-05 }}, 3rd Ed., Wiley, New York (2001).
  • Dichromatism: a phenomenon where the hue is dependent on concentration and thickness of the absorbing substance.
  • Hue: the color's direction from white, for example in a color wheel or chromaticity diagram.
  • Shade: a color made darker by adding black.
  • Tint: a color made lighter by adding white.
  • Value, brightness, lightness, or luminosity: how light or dark a color is.

See also

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External links and sources

  • ColorLab MATLAB toolbox for color science computation and accurate color reproduction (by Jesus Malo and Maria Jose Luque, Universitat de Valencia). It includes CIE standard tristimulus colorimetry and transformations to a number of non-linear color appearance models (CIE Lab, CIE CAM, etc.).
{{Sister project links|wikt=color|b=no|q=no|s=no|n=no|v=no|species=no|d=P462}} {{Color topics}}{{Authority control}}

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