Poor or deficient color vision is an inability to see the difference between certain colors, but color is still seen. Many people commonly use the term "colorblind" for this condition. But true colorblindness — in which everything is seen in shades of black and white — is rare.
Poor color vision is usually inherited. Men are more likely to be born with poor color vision. Most people with poor color vision can't distinguish between certain shades of red and green. Less commonly, people with poor color vision can't distinguish between shades of blue and yellow.
Certain eye diseases and some medications also can cause poor color vision.