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Glossary Design & Media

Colour blindness

Colour blindness, or colour vision deficiency, is a reduced ability to tell certain colours apart, most often red from green.

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In more detail

Roughly 1 in 12 men and 1 in 200 women have a red-green deficiency. Never use colour alone to carry meaning: add shapes, labels or patterns, and test designs with a simulator.

Try these tools

Color Blindness Simulator

Simulate protanopia, deuteranopia, tritanopia and achromatopsia on any image in your browser.

See also

  • Glossary Colour contrast
    Colour contrast is the difference in luminance between text and its background; WCAG expresses it as a ratio from 1:1 to 21:1.
  • Guide How Color and Contrast Work
    Hex, RGB and HSL are one colour, how the WCAG contrast ratio is computed with real pass and fail examples.
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