Color Blindness Simulator

Simulate how colors appear under 4 types of color vision deficiency

What is it and how does it work?

Color blindness (color vision deficiency) affects approximately 1 in 12 men and 1 in 200 women worldwide — around 300 million people. The most common forms are red-green color blindness: deuteranopia (missing green cone cells, ~6% of men), protanopia (missing red cone cells, ~2% of men), and deuteranomaly/protanomaly (shifted rather than absent cone response). Tritanopia (blue-yellow) and achromatopsia (complete color blindness) are much rarer.

Color blindness simulation tools apply mathematical color transformations to images, UI screenshots, or design mockups to show what they look like to people with specific types of color vision deficiency. This is essential in accessible design: if two states in your UI (error and success, for example) differ only in color, users with red-green color blindness cannot distinguish them. WCAG 2.1 guideline 1.4.1 requires that color not be the only visual means of conveying information.

Common use cases

• Form validation: test whether error states (red border + text) remain distinguishable from success states (green border + text) under deuteranopia — add an icon or pattern as a secondary cue if not.
• Chart color palettes: simulate your data visualization color scheme under different deficiency types — use ColorBrewer palettes designed specifically to be distinguishable under common color vision deficiencies.
• Map design: traffic maps that use red/yellow/green for congestion levels become ambiguous for red-green color blind users — simulate and switch to a blue/orange palette or add road pattern overlays.

Frequently asked questions

What is the difference between color blindness types?

Protanopia: no red cones, reds appear dark/black, can't distinguish red from green. Deuteranopia: no green cones, similar confusion but reds appear brighter. Protanomaly/deuteranomaly: shifted (not absent) cones causing mild-moderate difficulty. Tritanopia: no blue cones, confuses blue/yellow and blue/green. Achromatopsia: no functioning cone cells, sees only shades of gray.

What is the Ishihara test?

The Ishihara color test is the most widely used screening for red-green color blindness. It consists of plates of colored dots arranged to show a number visible to people with normal color vision but invisible (or showing a different number) to people with color blindness. A score of 9+ errors on 14 plates indicates color vision deficiency. Online Ishihara tests are not a clinical substitute for a proper ophthalmologist assessment.

How do I design accessible color schemes?

Key principles: (1) never use color as the only differentiator — add icons, patterns, or labels. (2) Ensure sufficient luminance contrast between foreground and background (WCAG minimum 4.5:1 for normal text). (3) Use color-blind-safe palettes: avoid red/green combinations for critical information. (4) Test with simulation tools before shipping. The most effective single palette change: replace pure red with orange-red (#FF4500 vs #FF0000) — more distinguishable under protanopia.

Can color blindness be corrected?

There is no cure. EnChroma glasses use notch filters to enhance the difference between the red and green signals reaching the eye — they work for some people with anomalous trichromacy (protanomaly/deuteranomaly) but not for dichromats (missing cones entirely). iOS and Android offer color filter accessibility modes. There is active research into gene therapy for color vision deficiency correction.

Utility

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