# Color Blindness Simulator

Simulate how colors look to people with protanopia, deuteranopia, tritanopia and achromatopsia. Paste up to 100 colors and get a table of hex values for each type of color vision deficiency, computed with the Machado, Oliveira and Fernandes model in culori, plus a severity setting for the milder anomalous forms. Useful for checking palettes, charts, maps and status colors before they ship.

## Frequently asked questions

### Which types of color blindness are simulated?

Protanopia (no working red cones), deuteranopia (no green cones), tritanopia (no blue cones) and achromatopsia (no color vision). Below 100% severity the columns are named for the anomalous forms: protanomaly, deuteranomaly, tritanomaly and achromatomaly.

### Which model is used?

For the three cone types, the physiologically based model by Machado, Oliveira and Fernandes (2009), with the precomputed matrices that culori ships. The matrices are applied to linear-light RGB, as the model specifies, and the result is converted back to sRGB. Achromatopsia replaces each color with the gray of the same relative luminance.

### What does the severity setting do?

100% simulates the complete dichromacy, lower values simulate the anomalous forms, and 0% returns the original color. The value is rounded to the nearest 10%, because the Machado matrices are published in 10% steps. For achromatopsia the severity blends between the color and its gray in linear light.

### How do I enter colors?

Enter one color per line, or several on one line separated by commas or semicolons; commas inside rgb() or hsl() do not split. Hex codes with or without #, CSS color names, rgb(), hsl(), hwb(), lab(), lch(), oklab(), oklch(), color() and cmyk() are accepted. You can check up to 100 colors per run.

### How accurate is the simulation?

It approximates average dichromat vision on a standard sRGB display. Real color vision varies from person to person, and display calibration and ambient light change what anyone sees. Use it to find colors that collapse into each other, not as a medical test.

### How common are these deficiencies?

Red-green deficiencies, the protan and deutan types, affect roughly 8% of men and 0.5% of women of Northern European descent, with deuteranomaly the most common. Tritan deficiencies and achromatopsia are rare, each affecting roughly 1 in 10,000 people or fewer.

### What should I do if two colors look the same?

Change their lightness, not only their hue, because lightness differences survive every type of color blindness. Also add a second cue such as a label, icon, pattern or position, which WCAG success criterion 1.4.1 asks for whenever color carries meaning.

### What happens to transparent and wide-gamut colors?

Colors outside sRGB, such as vivid Display P3 or OKLCH values, are first mapped into sRGB with the CSS Color 4 algorithm. Alpha is carried over to the results, so semi-transparent input gives 8-digit hex codes.

### Why does pure red turn olive for protanopia?

People with protanopia lack long-wavelength cones, so red appears much darker and shifts toward yellow-brown. In the model, #ff0000 becomes a dark olive of about #6d5f00, while deuteranopia keeps more brightness and gives a mustard tone of about #a39000.

### Can I check a whole image?

No, this tool works on color values, which keeps it fast and exact for palettes and design tokens. Pick the key colors of a design or chart and paste them here to compare the simulated columns side by side.

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