Color

Color effect – Sunlight shining through stained glass onto carpet (Nasir ol Molk Mosque located in Shiraz, Iran)
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 illusion.

Color (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).[1][2] 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.[3] 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.[4]

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).

Physics of color

Continuous optical spectrum rendered into the sRGB color space.
The colors of the visible light spectrum[5]
Color Wavelength
interval
Frequency
interval
Red ~ 700–635 nm ~ 430–480 THz
Orange ~ 635–590 nm ~ 480–510 THz
Yellow ~ 590–560 nm ~ 510–540 THz
Green ~ 560–520 nm ~ 540–580 THz
Cyan ~ 520–490 nm ~ 580–610 THz
Blue ~ 490–450 nm ~ 610–670 THz
Violet or Purple ~ 450–400 nm ~ 670–750 THz
Color, wavelength, frequency and energy of light
Color

(nm)

(THz)

(μm−1)

(eV)

(kJ mol−1)

Infrared >1000 <300 <1.00 <1.24 <120
Red 700 428 1.43 1.77 171
Orange 620 484 1.61 2.00 193
Yellow 580 517 1.72 2.14 206
Green 530 566 1.89 2.34 226
Cyan 500 505
Blue 470 638 2.13 2.64 254
Violet (visible) 420 714 2.38 2.95 285
Near ultraviolet 300 1000 3.33 4.15 400
Far ultraviolet <200 >1500 >5.00 >6.20 >598

Electromagnetic radiation is characterized by its wavelength (or frequency) and its intensity. When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 390 nm to 700 nm), it is known as "visible light".

Most light sources emit light at many different wavelengths; a source's spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, there are many more possible spectral combinations than color sensations. In fact, one may formally define a color as a class of spectra that give rise to the same color sensation, although such classes would vary widely among different species, and to a lesser extent among individuals within the same species. In each such class the members are called metamers of the color in question.

Spectral colors

The familiar colors of the rainbow in the spectrum—named using the Latin word for appearance or apparition by Isaac Newton in 1671—include all those colors that can be produced by visible light of a single wavelength only, the pure spectral or monochromatic colors. The table at right shows approximate frequencies (in terahertz) and wavelengths (in nanometers) for various pure spectral colors. The wavelengths listed are as measured in air or vacuum (see refractive index).

The color table should not be interpreted as a definitive list—the pure spectral colors form a continuous spectrum, and how it is divided into distinct colors linguistically is a matter of culture and historical contingency (although people everywhere have been shown to perceive colors in the same way[6]). A common list identifies six main bands: red, orange, yellow, green, blue, and violet. Newton's conception included a seventh color, indigo, between blue and violet. It is possible that what Newton referred to as blue is nearer to what today is known as cyan, and that indigo was simply the dark blue of the indigo dye that was being imported at the time.[7]

The intensity of a spectral color, relative to the context in which it is viewed, may alter its perception considerably; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive green.

Color of objects

The color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Physically, objects can be said to have the color of the light leaving their surfaces, which normally depends on the spectrum of the incident illumination and the reflectance properties of the surface, as well as potentially on the angles of illumination and viewing. Some objects not only reflect light, but also transmit light or emit light themselves, which also contributes to the color. A viewer's perception of the object's color depends not only on the spectrum of the light leaving its surface, but also on a host of contextual cues, so that color differences between objects can be discerned mostly independent of the lighting spectrum, viewing angle, etc. This effect is known as color constancy.

The upper disk and the lower disk have exactly the same objective color, and are in identical gray surroundings; based on context differences, humans perceive the squares as having different reflectances, and may interpret the colors as different color categories; see checker shadow illusion.

Some generalizations of the physics can be drawn, neglecting perceptual effects for now:

  • Light arriving at an opaque surface is either reflected "specularly" (that is, in the manner of a mirror), scattered (that is, reflected with diffuse scattering), or absorbed – or some combination of these.
  • Opaque objects that do not reflect specularly (which tend to have rough surfaces) have their color determined by which wavelengths of light they scatter strongly (with the light that is not scattered being absorbed). If objects scatter all wavelengths with roughly equal strength, they appear white. If they absorb all wavelengths, they appear black.[8]
  • Opaque objects that specularly reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences. An object that reflects some fraction of impinging light and absorbs the rest may look black but also be faintly reflective; examples are black objects coated with layers of enamel or lacquer.
  • Objects that transmit light are either translucent (scattering the transmitted light) or transparent (not scattering the transmitted light). If they also absorb (or reflect) light of various wavelengths differentially, they appear tinted with a color determined by the nature of that absorption (or that reflectance).
  • Objects may emit light that they generate from having excited electrons, rather than merely reflecting or transmitting light. The electrons may be excited due to elevated temperature (incandescence), as a result of chemical reactions (chemoluminescence), after absorbing light of other frequencies ("fluorescence" or "phosphorescence") or from electrical contacts as in light emitting diodes, or other light sources.

To summarize, the color of an object is a complex result of its surface properties, its transmission properties, and its emission properties, all of which contribute to the mix of wavelengths in the light leaving the surface of the object. The perceived color is then further conditioned by the nature of the ambient illumination, and by the color properties of other objects nearby, and via other characteristics of the perceiving eye and brain.

Other Languages
Afrikaans: Kleur
Alemannisch: Farbe
አማርኛ: ቀለም
Ænglisc: Bleoh
العربية: لون
aragonés: Color
ܐܪܡܝܐ: ܓܘܢܐ
armãneashti: Hromâ
অসমীয়া: ৰং
asturianu: Color
Atikamekw: Aicipekahikan
Avañe'ẽ: Sa'y
Aymar aru: Sami
azərbaycanca: Rəng
تۆرکجه: رنگ
বাংলা: রঙ
Bân-lâm-gú: Sek
башҡортса: Төҫ
беларуская: Колер
беларуская (тарашкевіца)‎: Колер
भोजपुरी: रंग
Bikol Central: Kolor
български: Цвят (оптика)
bosanski: Boja
brezhoneg: Liv
буряад: Үнгэ
català: Color
Чӑвашла: Тӗс
Cebuano: Kolor
čeština: Barva
Cymraeg: Lliw
dansk: Farve
Deutsch: Farbe
डोटेली: रङ्ङ
eesti: Värvus
Ελληνικά: Χρώμα
эрзянь: Тюс
español: Color
Esperanto: Koloro
estremeñu: Colol
euskara: Kolore
فارسی: رنگ
Fiji Hindi: Rang
français: Couleur
Frysk: Kleur
furlan: Colôr
Gaeilge: Dath
Gàidhlig: Dath
galego: Cor
贛語:
客家語/Hak-kâ-ngî: Ngân-set
한국어:
հայերեն: Գույն
हिन्दी: रंग
hrvatski: Boja
Ido: Koloro
Igbo: Àgwà
Ilokano: Maris
Bahasa Indonesia: Warna
interlingua: Color
íslenska: Litur
italiano: Colore
עברית: צבע
Basa Jawa: Warna
ಕನ್ನಡ: ಬಣ್ಣ
ქართული: ფერი
қазақша: Түс
Kinyarwanda: Ibara
Kiswahili: Rangi
Kreyòl ayisyen: Koulè
Кыргызча: Түс
Ladino: Kolor
лакку: Ранг
ລາວ: ສີ
Latina: Color
latviešu: Krāsa
Lëtzebuergesch: Faarf
лезги: Ранг
lietuvių: Spalva
Limburgs: Kluuer
lingála: Lángi
Lingua Franca Nova: Color
Livvinkarjala: Väri
la .lojban.: skari
Luganda: Langi
lumbaart: Culur
magyar: Szín
मैथिली: रङ्ग
македонски: Боја
മലയാളം: നിറം
मराठी: रंग
مصرى: لون
Bahasa Melayu: Warna
Mìng-dĕ̤ng-ngṳ̄: Ngàng-sáik
мокшень: Тюс
монгол: Өнгө
မြန်မာဘာသာ: အရောင်
Nāhuatl: Tlapālli
Nederlands: Kleur
Nēhiyawēwin / ᓀᐦᐃᔭᐍᐏᐣ: Itasinâsowin
नेपाली: रङ्ग
नेपाल भाषा: रङ्ग
日本語:
norsk: Farge
norsk nynorsk: Farge
Nouormand: Couoleû
occitan: Color
oʻzbekcha/ўзбекча: Rang
ਪੰਜਾਬੀ: ਰੰਗ
پنجابی: رنگ
پښتو: رنگ
Patois: Kola
Tok Pisin: Kala
Plattdüütsch: Klöör
polski: Barwa
português: Cor
română: Culoare
Runa Simi: Llimphi
русиньскый: Фарба
русский: Цвет
संस्कृतम्: वर्णः
Scots: Colour
Seeltersk: Faawe
shqip: Ngjyra
sicilianu: Culuri
සිංහල: පාට
Simple English: Colour
سنڌي: رنگ
SiSwati: Bâla
slovenčina: Farba (fyzika)
slovenščina: Barva
Soomaaliga: Midab
کوردی: ڕەنگ
српски / srpski: Боја
srpskohrvatski / српскохрватски: Boja
Basa Sunda: Warna
suomi: Väri
svenska: Färg
Tagalog: Kulay
தமிழ்: நிறம்
татарча/tatarça: Төс
తెలుగు: రంగు
ไทย: สี
тоҷикӣ: Ранг
ᏣᎳᎩ: ᏗᎧᏃᏗ
Türkçe: Renk
удмурт: Буёл
українська: Колір
اردو: رنگ
vèneto: Cołor
vepsän kel’: Muju
Tiếng Việt: Màu sắc
Võro: Värm
walon: Coleur
Winaray: Kolor
Wolof: Melo
吴语: 顏色
Xitsonga: Mihlovo
ייִדיש: קאליר
粵語:
žemaitėška: Spalva
中文: 颜色