 trichromacy or trichromaticism is the condition of possessing three independent channels for conveying color information, derived from the three different cone types.color glossary organisms with trichromacy are called trichromats. 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. in actuality the number of such receptor types may be greater than three, since different types may be active at different light intensities. in vertebrates with three types of cone cells, at low light intensities the rod cells may contribute to color vision. ==humans and other animals that are trichromats== humans and some other mammals have evolved trichromacy based partly on pigments inherited from early vertebrates. in fish and birds, for example, four pigments are used for vision. these extra cone receptor visual pigments detect energy of other wavelengths, including sometimes ultraviolet. eventually two of these pigments were lost (in placental mammals) and another was gained, resulting in trichromacy among some primates. humans and closely related primates are usually trichromats, as are some of the females of most species of new world monkeys, and both male and female howler monkeys. recent research suggests that trichromacy may also be quite general among marsupials.arrese, ca; oddy, ay; runham, pb; hart, ns; shand, j; hunt, dm (2005). "cone topography and spectral sensitivity in two potentially trichromatic marsupials, the quokka (setonix brachyurus) and quenda (isoodon obesulus)." proceedings of the royal society of london series b. 272(1595), 791-796. 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. the possibility of trichromacy in marsupials potentially has another evolutionary basis than that of [[
Color Visual_system