What makes a person color blind?

A genetic mutation: A person is born color blind because he has a mutation in the genes that are needed to see certain colors the way a normal person sees colors. Most color blind people can see many colors, but the colors appear in a "different" hue, compared with how the colors appear to a normal person. Very rarely does anyone have total color blindness and see only black, white, and gray.

Genetics: Several genes are responsible for allowing our retinas' receptors to record the different colors we see. Occasionally, someone develops a mutation that prevents some of the colors to be recorded. This makes differentiating certain shades or colors difficult.

Several causes: Most color deficient persons have an inherited change in their light receptors limiting color discrimmination. Advanced diabetics frequently have enough retina destroyed to lower their color recognition. Diseases of the optic nerve such as multiple sclerosis can impair color recognition. There are rare strokes which can also diminish color recognition.