Online color blindness tests, such as the Ishihara test, can suggest if a person has a type of color blindness. It may reveal difficulty distinguishing between two colors or in rarer cases ...

A person with monochromatic color blindness does not see any colors — they see only black, white, and gray. With dichromatic color blindness, a person sees two colors out of red, green, and blue ...

People with color blindness have color vision defects due to a partial or total lack of cones in the retina. Without these cones, it is difficult to tell the difference between red, green, and blue.

The baseline for normal red-green vision is typically considered scoring a 17 or higher on plates 1 through 21. The man’s self-reported score before the mushroom test was 14.

Berkeley-based company EnChroma, which makes glasses that enrich color vision for the colorblind. Erik Ritchie is the company’s CEO, and he shares his vision for the future of seeing in color.

At least eight in 100 men (8%) and one in 200 women (0.5%) suffer from red-green color vision deficiency (CVD), totaling 13 million in the U.S. and 350 million worldwide.