Trichromacy

Trichromacy or trichromatism is the possession of three independent channels for conveying color information, derived from the three different types of cone cells in the eye.

The normal explanation of trichromacy is that the organism's retina contains three types of color receptors (called cone cells in vertebrates) with different absorption spectra.

Humans and some other mammals have evolved trichromacy based partly on pigments inherited from early vertebrates.

These extra cone receptor visual pigments detect energy of other wavelengths, sometimes including ultraviolet.

[4] A study conducted regarding trichromacy in Australian marsupials suggests the medium wavelength sensitivity (MWS), cones of the honey possum (Tarsipes rostratus) and the fat-tailed dunnart (Sminthopsis crassicaudata) are features coming from the inherited reptilian retinal arrangement.

[5] Most studies of carnivores, as of other mammals, reveal dichromacy; examples include the domestic dog, the ferret, and the spotted hyena.

[3] Research indicates that trichromacy allows animals to distinguish brightly colored fruit and young leaves from other vegetation that is not beneficial to their survival.

On the other hand, the L and M cones are hard to distinguish by their shapes or other anatomical means – their opsins differ in only 15 out of 363 amino acids, so no one has yet succeeded in producing specific antibodies to them.

Close-up of a trichromatic in-line shadow mask CRT display , which creates most visible colors through combinations and different levels of the three primary colors : red, green and blue
Normalised responsivity spectra of human cone cells
Illustration of color metamerism:
In column 1, a ball is illuminated by monochromatic light. Multiplying the spectrum by the cones' spectral sensitivity curves gives the response for each cone type.
In column 2, metamerism is used to simulate the scene with blue, green and red LEDs, giving a similar response.