Color blindness is a disease that makes it difficult for people to tell the difference between some colors. Another more accurate name for the disorder is color blindness, since it is extremely rare for someone to be completely color blind by doing color blind test. People see colors because they are born with three types of light-sensitive cones in their eyes. Each cone type is sensitive to light of different wavelengths. These wavelengths are red, blue and green. Dyschromatopsia is a rare acquired inability to discriminate colors by hue. Dyschromatopsia is most often associated with damage to the inferior part of the occipital lobes, in the fusiform gyrus. This corresponds to the area identified in functional experiments as the human color area (V4).Patients usually have difficulty in tasks such as sorting sets of colored counters. Hemidyschromatopsia may be more common; reflecting the location of damage, there is often an associated superior quadrantanopia on the same side. Color anomia is a disorder in which patients present with an inability to name colors but are still able to sort colored counters and differentiate between colors despite failure to name them.