The inability of the cone cells in the retina to correctly detect one or more of the red, green or blue light spectra is called color blindness, according to the American Academy of Opthamology. Lack of color distinction between red and green colors is the most common form of color blindness.
Cone cell color detection problems are caused by one or more cells either being absent, not functioning correctly or detecting a different color than is normal. Deuteranopia is the inability to see green, while protanopia doesn't detect red and tritinopia is a blue deficiency, according to Colour Blind Awareness. Achromatopsia, or only seeing shades of gray, is very rare.
Most color blindness is genetic, states WebMD, but later-life onset does occur. The most common causes for later onset include aging and eye problems such as glaucoma, macular degeneration, cataracts or diabetic retinopathy. An eye injury or the side effects of a medicine can also cause color blindness.
Testing and diagnosis for color blindness is most often done by using the Ishihara Plate test, Colour Blind Awareness explains. The test features 38 plates of circles created by irregular colored dots in two or more colors, with one of the colors in a number pattern. Some plates have color combinations for normal vision, while some have layouts that only colorblind people can see.