What Is a Color Blindness Simulator?
A color blindness simulator shows you how your colors appear to people with different types of color vision deficiency. Approximately 8% of men and 0.5% of women have some form of color blindness — that's roughly 300 million people worldwide. If your design relies on color alone to convey information, a significant portion of your audience may not see it correctly. Color blindness coverage is one accessibility layer; gamut coverage is another. The Gamut Mapper checks whether your colors render correctly across sRGB, Display P3, and Rec2020.
This tool simulates protanopia, deuteranopia, tritanopia, and other deficiency types in real time, letting you evaluate any color combination before shipping your design.
Types of Color Vision Deficiency
Protanopia — reduced sensitivity to red light. Reds appear darker and shift toward green/brown. Deuteranopia — reduced sensitivity to green light. The most common type. Greens shift toward red/brown. Tritanopia — reduced sensitivity to blue light. Rare. Blues appear greenish, yellows appear pink. Achromatopsia — complete color blindness. Extremely rare. Only grayscale vision.
How to Use This Color Blindness Simulator
- Enter your colors — Input the foreground and background colors you want to test — paste hex codes or use the color picker.
- View all simulations — The tool shows how your color combination appears under all major types of color vision deficiency — deuteranopia, protanopia, tritanopia, and achromatopsia.
- Check for problem pairs — Identify combinations where the simulated versions lose distinguishability — this indicates an accessibility issue.
- Adjust and retest — Modify your colors until all simulations show adequate differentiation between foreground and background.
Tips and Best Practices
- → Don't rely on color alone. Always pair color with another visual cue — icons, patterns, labels, or underlining. This ensures information is accessible regardless of color perception.
- → Red-green is the most common deficiency. About 8% of men and 0.5% of women have red-green color blindness (deuteranopia/protanopia). Always test red-green combinations.
- → Blue-yellow deficiency is rare but exists. Tritanopia affects about 0.01% of the population. Still worth testing, especially for data visualizations and dashboards.
- → Use our Contrast Checker too. Color blindness simulation shows how colors are perceived; contrast checking verifies they're readable. Both are needed for full accessibility testing. Try our Contrast Checker.
Frequently Asked Questions
What is color blindness?
Color vision deficiency affects ~8% of men and ~0.5% of women. The most common types are protanopia and deuteranopia (red-green), followed by tritanopia (blue-yellow). Affected individuals perceive certain color combinations as identical.
Why should I test for color blindness?
~300 million people have color vision deficiency. If your design uses color alone to convey meaning (red=error, green=success), these users can't distinguish the difference. Testing ensures your interface works for everyone.
How do I make designs color-blind friendly?
Never rely on color alone. Pair colors with text labels, icons, or patterns. Use high-contrast combinations. Test with a simulator. Choose colors distinguishable across all deficiency types.
What is color blindness?+
Color blindness (color vision deficiency) is a reduced ability to distinguish certain colors. The most common types are deuteranopia and protanopia (red-green deficiency, affecting ~8% of men), tritanopia (blue-yellow deficiency), and achromatopsia (total color blindness). It's overwhelmingly genetic and affects about 1 in 12 men and 1 in 200 women.
How does color blindness affect web design?+
Users with color vision deficiency may not be able to distinguish your link colors from body text, tell apart chart colors, recognize error states (red) vs. success states (green), or see warning indicators that rely on color alone. Inclusive design uses color plus additional visual cues.
What WCAG guidelines address color blindness?+
WCAG 2.1 Success Criterion 1.4.1 (Use of Color) states that color must not be the only visual means of conveying information. Success Criterion 1.4.11 (Non-text Contrast) requires 3:1 contrast for UI components. These guidelines ensure accessibility for users with color vision deficiency.
Which WCAG criteria address color vision deficiency?+
Never use color as the only indicator of meaning. Pair colors with text labels, icons, or patterns. Use high-contrast color combinations. Test your palette with a simulator like this one. Choose colors that remain distinguishable across all deficiency types.
How accurate are color-blindness simulations?+
Simulations use peer-reviewed transformation matrices (Brettel-Vienot-Mollon for dichromacy and Machado for anomalous trichromacy) that approximate how the most common types of color vision deficiency perceive sRGB pixels. They are a reliable proxy for design review but they are not a medical diagnostic — actual perception varies between individuals with the same diagnosis, and the simulation cannot model adaptation, lighting, or contextual cues.
Which type of color blindness should I prioritize testing for?+
Deuteranomaly (reduced sensitivity to green) is the most common form, affecting roughly 5 percent of men of European descent, so it is the highest-impact case to test. Protanopia and protanomaly (red deficiency) follow. Tritanopia (blue deficiency) is rare but worth a check for anything that pairs blue and green or relies on yellow-blue contrast. Total color blindness (achromatopsia) is rare enough that grayscale preview is usually a sufficient proxy.
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