Color blindness is a condition in which a person has difficulty distinguishing certain colors under normal lighting conditions. This decreased ability to see color is usually a developmental defect in some sets of retinal cones, which are responsible for color perception. It's caused by a genetic defect that follows an X-linked inheritance pattern.
Most people with color blindness can see some form of color, but they may not be able to identify all the colors they see. In addition, some people with this condition may confuse different shades of the same color or have difficulty distinguishing between specific colors and shades.