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Kordu Tools
Colour Tools Runs in browser Updated 08 Apr 2026

Color Blindness Simulator

See how any color appears under different types of color blindness — protanopia, deuteranopia, tritanopia, and achromatopsia.

Dark color
Each card shows how your color appears to someone with that type of color blindness. The ΔE value approximates the perceived color difference — lower means harder to distinguish from the original.

Original

#3B82F6

Protanopia

#5A5ADA

Protanopia (Red-blind)

No functional red (L) cones. Reds appear very dark; red-green confusion is severe.

ΔE approx.

33

Prevalence: ~1% of males

Original

#3B82F6

Deuteranopia

#5650D3

Deuteranopia (Green-blind)

No functional green (M) cones. Similar confusion to protanopia but greens are not darkened.

ΔE approx.

39

Prevalence: ~1% of males

Original

#3B82F6

Tritanopia

#3FC4BF

Tritanopia (Blue-blind)

No functional blue (S) cones. Blues and greens appear similar; blue-yellow confusion.

ΔE approx.

50

Prevalence: ~0.01% of people

Original

#3B82F6

Achromatopsia

#7A7A7A

Achromatopsia (Total color blindness)

No functional cone cells. Vision is entirely grayscale, often with extreme light sensitivity.

ΔE approx.

80

Prevalence: ~0.003% of people
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How to use Color Blindness Simulator

  1. Enter a color

    Use the color picker or type a hex code (e.g. #3b82f6) into the input field.

  2. Review the simulations

    Each card shows how your color appears under protanopia, deuteranopia, tritanopia, and achromatopsia, with the simulated hex code.

  3. Adjust your palette

    If simulated colors are too similar to distinguish, adjust your design to improve accessibility for color-blind users.

Color Blindness Simulator FAQ

What is color blindness?
Color blindness (color vision deficiency) is the inability to distinguish certain colors. It is caused by absent or malfunctioning cone cells in the retina. The most common form is red-green color blindness, which affects about 8% of males and 0.5% of females of northern European descent.

How accurate is this simulation?
The simulation uses the Viénot et al. matrix transform method applied in sRGB space — a well-established practical approximation used by most color blindness tools. It is accurate for pure forms of each condition. Partial color blindness (anomalous trichromacy) is not simulated here.

Why does red appear so dark in protanopia?
Protanopes have no red (L) cone cells. Red light contributes very little perceived brightness without L cones — so reds appear nearly black or very dark brown, unlike in deuteranopia where reds appear more yellowish.

What does the ΔE value mean?
ΔE (delta E) approximates the perceptual difference between the original color and the simulated color. A value near 0 means the colors appear nearly identical to that person — a sign that color alone may not be a reliable signal in your design. Values above 30 mean the difference remains visible.

Is this tool suitable for WCAG compliance?
This tool helps you understand how your colors appear to color-blind users, which is important for WCAG 1.4.1 (Use of Color). For WCAG contrast ratio requirements (1.4.3/1.4.6), use the Contrast Checker tool.

Is my data sent anywhere?
No. All simulation happens in your browser. Nothing is uploaded or stored.

Background

The Kordu Color Blindness Simulator shows how any color appears to people with different types of color vision deficiency. Enter a hex code or use the color picker, and the tool instantly generates simulations for all four major types:

  • Protanopia — no functional red (L) cones; affects ~1% of males. Reds appear very dark and are confused with greens.
  • Deuteranopia — no functional green (M) cones; affects ~1% of males. Similar red-green confusion to protanopia but without the darkening of reds.
  • Tritanopia — no functional blue (S) cones; affects ~0.01% of people. Blues and greens appear similar; blue-yellow confusion.
  • Achromatopsia — no functional cone cells; affects ~0.003% of people. Vision is entirely grayscale.

Each simulation card shows the original color alongside the simulated perception, with the perceived hex value and an approximate perceptual difference score. Lower scores mean the simulated color is harder to distinguish from the original.

Color simulations use the Viénot et al. matrix transform method applied directly in sRGB space. This is a well-established practical approximation.

Common uses: accessibility testing for UI design, verifying that color choices work for color-blind users, and understanding WCAG contrast requirements in context.

All simulation runs client-side in your browser. Nothing is uploaded or stored.

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