Most people use the term "Color Blind" when they actually mean a Color Vision Deficiency. It is extremely rare for people to be totally color blind. Color Vision Deficiency occurs in 4 out of 100 males (men) and less than 1 out of 100 females (women). There are two different types of cells in the retina; the cones, which discriminate color are concentrated in the center of the retina, and the rods which help us detect movement, and are mostly concentrated in the periphery that tells us about our side vision.
Specially tinted contact lenses can often enable people to better distinguish between colors. In addition to the standard testing that is needed in order to determine the measurements for a contact lens (corneal curvature, power, etc) testing is done to determine if one or two lenses are needed, the intensity of the tint, the width of the pupil zone of the lens, etc.