How many people are color blind?
The term “color blindness” is too vague to be useful. There are 7 types of color deficiency due to cone abnormalities. In addition, the elderly see colors differently, but are not color blind in the usual sense of the term. Finally, brain damage can create a very rare condition called achromatopsia. People with normal color vision are called “trichromats” because they require three primaries to match any arbitrary sample. The trichromatic eye has three cone types, each containing a photopigment which responds to a restricted range of wavelengths. The major color deficiencies are abnormalities in the way cone pigment is distributed in the cones. In all, there are three deficit classes: Anomalous Trichromats There is a subpopulation of trichromats, who still requires three primaries to match a sample, but whose matches are abnormal because they use one primary far more than would be expected. While having all three cone types, one cone type is rarer, has a reduced amount of pigment, or h
