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Color blindness simulator

See how a color looks to someone with color vision deficiency.

Input
100
Output
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Color blindness simulator
Paste one color per line and this tool shows how it looks to someone with a color vision deficiency, alongside the original. It converts each color to LMS cone-response space, applies a simulation matrix for the chosen deficiency, then converts back — the same approach used by professional accessibility tooling, running entirely on your machine.
Choose the deficiency type from the eight most common forms: protanopia, deuteranopia and tritanopia are complete loss of the red, green or blue cone response; protanomaly, deuteranomaly and tritanomaly are the milder "weak" versions that are far more common in practice; achromatopsia and achromatomaly simulate total and partial color blindness. The strength slider dials the effect from 0% (unchanged) to 100% (the full simulated effect), useful for showing a spectrum of severity rather than a single worst case. Output prints in HEX, RGB or HSL, with a small swatch next to each value so the difference is visible, not just readable.
Write two colors on a line — a foreground and a background, in either order — and the tool also reports the WCAG contrast ratio between them before and after simulation, with a pass/fail against the 4.5:1 AA threshold. That catches a common failure: a design with enough contrast for typical vision that collapses toward unreadable once red and green, or blue and yellow, become hard to tell apart. Colors can be written as hex, rgb()/rgba(), hsl()/hsla(), or common CSS names; a line with none recognized is kept as a short note rather than dropped.
Everything runs locally in your browser — no color or design file is ever uploaded. Copy the result, download it as a .txt file, or send it back into the input to check another palette against a different deficiency type.
FAQ
Which deficiency type should I check first?
Deuteranopia and deuteranomaly (reduced or missing green response) are the most common forms by a wide margin, followed by the protan (red) types. Tritanopia and tritanomaly (blue) are rare. Checking all three color axes gives the fullest picture.
What's the difference between protanopia and protanomaly?
Protanopia is a complete absence of the red-sensing cone response; protanomaly is a shifted, weaker version of it. The "-anomaly" forms are the milder and much more common condition — full dichromacy is comparatively rare.
How is the simulation calculated?
Each color is converted from RGB into LMS cone-response space, the missing or shifted cone response is reconstructed from the other two using a fixed simulation matrix, and the result is converted back to RGB. Achromatopsia is modeled separately as a luminance-based grayscale, since there is no single cone loss to simulate there.
Can I check contrast between two colors after simulation?
Yes. Write two colors on one line — a text color and a background, for example — and the tool reports the WCAG contrast ratio both before and after the simulated deficiency, so you can see whether a passing combination still holds up.
Are my colors uploaded anywhere?
No. The simulation runs entirely in your browser using JavaScript — nothing you paste in is sent to a server.