What are Protanopia, Deuteranopia, and Tritanopia?

Protanopia is reduced sensitivity to red light. Deuteranopia is reduced sensitivity to green light, the most common form of colour blindness. Tritanopia is reduced sensitivity to blue light, the rarest form. Each type changes how certain colour combinations appear.

How do I check if my design works for colorblind users?

Use the colourblind simulation toggle on the contrast checker's live preview to see your colours filtered for Protanopia, Deuteranopia, and Tritanopia. Also ensure you never rely on colour alone to convey information — pair colour with icons, labels, or patterns.

Colorblind Contrast Checker —
Free Color Vision Simulator

Simulate how your colour palette appears to people with Protanopia, Deuteranopia, and Tritanopia. Free, instant, no signup required.

3 colour blindness types Live preview No signup

Open the Colorblind Simulator

Click the Protanopia, Deuteranopia, or Tritanopia pill in the live preview to see your colours simulated.

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Understanding the 3 Main Types of Color Blindness

Most Common

Deuteranopia (Red-Green)

Reduced sensitivity to green light. The most common form of colour blindness, affecting around 1 in 20 men. Reds, greens, and browns can appear similar.

Common

Protanopia (Red-Green)

Reduced sensitivity to red light. Similar effects to Deuteranopia — reds can appear darker and harder to distinguish from greens and browns.

Rare

Tritanopia (Blue-Yellow)

Reduced sensitivity to blue light. Much rarer than red-green colour blindness. Blues and greens, or yellows and violets, can be hard to distinguish.

Designing for Colorblind Users — Best Practices

Never rely on colour alone to convey information. The most common accessibility failure for colourblind users isn't poor contrast — it's using colour as the only signal for status, errors, or required fields. A red error message should also have an icon and text label; a "required" form field should have an asterisk, not just a red border.

Test your full design — not just isolated colour pairs — using the colourblind simulation toggle in our contrast checker's live preview. This shows your actual buttons, links, and layout filtered for each colour vision type, giving a far more realistic picture than testing swatches in isolation.

Colorblind Checker — FAQ

Colour blindness affects roughly 1 in 12 men and 1 in 200 women worldwide — predominantly red-green colour blindness (Protanopia and Deuteranopia). Blue-yellow colour blindness (Tritanopia) is much rarer.

Protanopia is reduced sensitivity to red light. Deuteranopia is reduced sensitivity to green light, the most common form. Tritanopia is reduced sensitivity to blue light, the rarest form.

Use the colourblind simulation toggle on the contrast checker's live preview to see your colours filtered for each type. Also ensure you never rely on colour alone to convey information.

Colorblind Contrast Checker —Free Color Vision Simulator