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British standard spelling of color blindness.

Example of an Ishihara color test plate. Viewers with normal color vision should clearly see the number "74".

British standard spelling of color blindness.

These color charts show how different color blind people see compared to a person with normal color vision.

British standard spelling of color blindness.

Illustration of the distribution of cone cells in the fovea of a normal trichromatic retina (left), and a protanopic retina. The center of the fovea holds very few blue-sensitive cones.