Colours (Commonwealth English), or colors (American English), are characteristics of human visual perception described through colour categories, with names such as red, orange, yellow, green, blue, or purple. 

Additive color mixing (using pure light): combining red and green yields yellow; combining all three primary colors together makes white.

This perception of different colours derives from the stimulation of cone cells in the human eye by electromagnetic radiation in the visible spectrum. 

Colour categories and physical specifications of colours 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.

Subtractive color mixing (using pigments like paint): combining yellow and magenta yields red; combining all three primary colors together makes black

Colour space

Colours can be identified numerically by coordinates called a colour space, which in 1931 were also named in global agreement with internationally agreed colour names like mentioned above (red, orange, etc.) by the International Commission on Illumination. 

The RGB colour space for instance is a colour 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). 

There may also be more than three colour dimensions in other colour spaces, such as in the CMYK colour model, wherein one of the dimensions relates to a colour's colourfulness).

Colour perception in other animals

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.

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.

Science of Colour

The science of color is sometimes called chromatics, colorimetry, or simply color science. It includes the study of the perception of colour 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).

Source adapted from: Wikipedia contributors. (2019, January 14). Color. In Wikipedia, The Free Encyclopedia. Retrieved 23:42, January 14, 2019, from