Color Blindness Simulator
See how your colors look to viewers with each type of color vision deficiency, and find the pairs that stop being distinguishable. Around 8% of men and 0.5% of women have some form of color vision deficiency, so most palettes are seen this way by someone. Everything runs in your browser.
Types of Color Vision Deficiency
Prevalence figures describe the general population and vary by ancestry. Red-green deficiencies are carried on the X chromosome, which is why they are far more common in men; tritan deficiencies and achromatopsia are not sex-linked.
| Type | Prevalence | What changes |
|---|---|---|
| Protanopia (no red cones) | About 1% of men | The long-wavelength (red) cone is absent. Reds darken noticeably and red, orange, and green become hard to tell apart. |
| Protanomaly (weak red cones) | About 1% of men | The red cone is shifted toward green. Reds look duller and darker, and red-green pairs lose separation without disappearing entirely. |
| Deuteranopia (no green cones) | About 1% of men | The medium-wavelength (green) cone is absent. Greens and reds collapse toward a shared yellow-beige axis. |
| Deuteranomaly (weak green cones) | About 5% of men — the most common form | The green cone is shifted toward red. This is the most common color vision deficiency and the one most interface color choices need to survive. |
| Tritanopia (no blue cones) | Fewer than 1 in 10,000, and not sex-linked | The short-wavelength (blue) cone is absent. Blue and green become confusable, and yellow can read as pink or grey. |
| Tritanomaly (weak blue cones) | Rare, and not sex-linked | The blue cone is shifted. Blue-green and yellow-red distinctions weaken without collapsing completely. |
| Achromatopsia (no color vision) | Roughly 1 in 30,000 | No usable cone response. Only lightness differences remain, which is the strictest test of whether a design relies on color alone. |
| Achromatomaly (partial color vision) | Rare | Heavily reduced but not absent color response, shown as a partial desaturation. |
How to Use the Color Blindness Simulator
Add the colors from your palette, chart series, or interface states — hex codes, rgb() values, and CSS color names all work. Every type of color vision deficiency is rendered side by side, so you can see at a glance where a palette collapses. Select a row to see each color before and after, and to get a list of the pairs that stop being distinguishable.
Understanding Color Vision Deficiency
Typical color vision uses three cone types, sensitive to long (red), medium (green), and short (blue) wavelengths. When one is missing the result is dichromacy: protanopia, deuteranopia, or tritanopia. When one is shifted rather than absent the result is anomalous trichromacy, which is more common and milder. Red-green deficiencies are by far the most frequent and are sex-linked, which is why they affect around 8% of men and under 1% of women.
Designing Palettes That Survive
Two rules cover most cases. First, never let color be the only signal: pair a red error state with an icon and a message, and label chart series directly rather than relying on a legend. Second, vary lightness as well as hue — two colors that differ in lightness stay distinguishable under every simulation here, including achromatopsia. Blue is the most reliable hue to differentiate against, which is why it dominates data visualisation.
Method and Limitations
Dichromatic simulation converts your color to linear sRGB, then to LMS cone-response space using the Hunt-Pointer-Estevez matrix normalised to D65, projects it onto the plane of colors the missing cone type cannot distinguish, and converts back. This follows Viénot, Brettel & Mollon (1999).
Anomalous trichromacy is shown as a 60% interpolation toward the matching dichromacy. Real anomalous trichromacy varies widely in severity between individuals, so treat that view as indicative rather than exact. Achromatopsia uses luminance-preserving desaturation with the Rec. 709 coefficients that match WCAG relative luminance.
Simulation shows how colors shift, not what a person perceives — someone with lifelong deuteranopia does not experience their vision as a filtered version of anyone else's. Use this to catch palettes that rely on hue alone, then confirm with the contrast checker and with real users.
Frequently Asked Questions about Color Blindness Simulator
The three dichromatic types use the Viénot, Brettel and Mollon LMS projection model, which is the method most simulation tools are built on. Anomalous types (protanomaly, deuteranomaly, tritanomaly) are shown as partial versions of the matching dichromacy — a widely used approximation, not a model of any specific person, since the severity of anomalous trichromacy varies from person to person.
Keep the color moving
Useful next steps
Your latest color stays in the local workspace when the next tool uses it.