How color blindness simulator works
Color vision deficiency affects roughly 1 in 12 men and 1 in 200 women. It comes in types named after the cone cells that misbehave: protan defects reduce red perception, deutan defects reduce green perception, tritan defects reduce blue perception, and achromatopsia removes color vision almost entirely. Each type has a complete form (-opia) and a partial form (-omaly), which is why the tool shows eight simulations rather than three.
The simulation applies the transformation matrices published by Machado, Oliveira and Fernandes (2009) — the standard reference for dichromat and anomalous-trichromat simulation — to the red, green and blue channels of your hex color, clamping the result back into the visible gamut. Achromatopsia is computed as BT.709 luminance greyscale, and achromatomaly as a half-way blend between the original color and that grey, so partial conditions genuinely sit between normal vision and the complete form.
Use it to sanity-check brand colors, chart series, status badges, and buttons: two colors that look clearly different to you may collapse to near-identical tones under deuteranopia — red and green being the classic trap. Click any swatch to copy its simulated hex, and pair the results with the site's color contrast checker, because simulating a deficiency and measuring luminance contrast are complementary accessibility checks.