Color blindness is the word used to describe mild to severe difficulties with identifying various colors and shades of colors. It is a misleading term because colorblind people are not blind. Rather, they tend to confuse some colors, and a rare few may not see colors at all.

Normal color vision requires the use of special cells, called cones, located in the retina of the eye. There are three types of cones, termed red, blue, and green, which enable people to see a large spectrum of colors. A defect or deficiency of any of the types of cones will result in abnormal color vision.

Red/green color blindness is the most common deficiency, affecting 8% of Caucasian males and 0.5% of females. People with red/green color blindness can often distinguish red or green if they can visually compare the colors. For example, they can pick out red...