Dichromasy

DICHROMASY, a form of color blindness, daltonism (see). For a normally sighted person, all the variety of perceived color shades can be obtained by mixing three basic colors in different proportions. For a certain class of color-blind individuals, their entire range of color sensations can be achieved by mixing two basic tones. Hence the names: trichromats and dichromats. Persons for whom the result of mixing three basic colors differs from the normal are called anomalous trichromats. Kries divides dichromats into two groups: protanopes and deuteranopes. For the former, mixing a larger amount of red color with a small amount of green produces a dark yellow sensation, while with the reverse proportion it produces a light yellow sensation. For deuteranopes, on the contrary, the first mixture is light and the second is dark.