Color blindness or color vision deficiency is the inability to distinguish certain shades of color or in more severe cases, see colors at all. The term "color blindness" is also used to describe this visual condition, but very few people are completely color blind Most people with color vision deficiency can see colors, but they have difficulty differentiating between
-> particular shades of reds and greens (most common) or
-> blues and yellows (less common).
People who are totally color blind, a condition called achromatopsia, can only see things as black and white or in shades of gray