Color blindness
It is the weakness of color perception. It is not a form of blindness, but there is difficulty distinguishing certain colors, such as red and green or blue and yellow.
Red-green color blindness is the most common form. Less common is the inability to perceive the blue-yellow color.
Cause
The problems caused in this case are due to a partial or complete lack of light-sensitive photoreceptors (cones) in the retina (the light-sensitive membrane at the back of the eye). Normally, there are three types of cones, the first type recognizes the color red, the second the color green and the third the color blue.
There are different degrees of the condition, the most common being partial color blindness, also called dyschromia. In the most severe form of color blindness (extremely rare) all colors are perceived as different shades of gray.