What is Color Blindness

Color blindness is lack of color vision so when a person can't distinguish some colors. It does not necessarily mean seeing only black and white (also called monochromacy = total color blindness). Some people can't simply recognize one certain color. For instance, they don't know the difference between red and green. That's why most "colorblind" people can actually see many colors, however, they can't tell a few specific ones.

Our eyes have three color receptors - red, green and blue. That's why our color vision issues are naturally based on those 3 colors and their mixtures. The following pictures depict what the color blind see when they look at colors of rainbow.

healthy eyes

Normal color vision

missing green

Absence of green retinal photoreceptors (deuteranope)

missing red

Absence of red retinal photoreceptors (protanope)

missing blue

Absence of blue retinal receptors (tritanope)

How Do You Get Color Blind

Color vision deficiencies can be acquired (eg. by accidents), however, they are usually inherited. Approximately 8% of men and 0.5% of women are color blind. So the chances are quite high that you know some color blind men. Most people have problems to tell green color from red.

Color Blind Tests

Color Blind Tests, also called "Ishihara Color Test", are eye exams commonly used by optometrists and eye doctors which can determine defect of red-green color vision. You are presented with a few colored plates each containing colored dots. Your task is to identify a pattern (eg. number or letter) made out of the dots.

1st Color Blindness Test

Can you see a "12" on this plate?
Number 12
Click to Enlarge

2nd Color Blindness Test

There is a "26" on this plate.
Number 26
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3rd Color Blindness Test

Can you trace a line from one "X" to the other?
Trace the Line
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4th Color Blindness Test

You should see 58 (upper left), 18 (upper right), E (lower left) and 17 (lower right).
Are you color blind?
Click to Enlarge


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