Color Blindness Simulator

Color vision deficiency affects about 1 in 12 men and 1 in 200 women. The three common types — protanopia, deuteranopia, and tritanopia — each shift specific cone responses, collapsing red/green or blue/yellow distinctions.

This simulator applies published transformation matrices to any input color or image, producing the approximate appearance under each deficiency. Use it for accessibility audits and palette validation.

The transforms come from the Brettel-Viénot-Mollon line of research published in the 1990s, refined by Machado and others. Each deficiency is modeled as a projection in LMS color space — the coordinate system describing the response of long, medium, and short-wavelength cones. Protanopia projects onto a plane that removes the L-cone axis; deuteranopia removes the M-cone axis; tritanopia removes the S-cone axis. The result is converted back through XYZ to sRGB for display. Anomalous trichromacy (the partial-deficiency variants) blends the dichromatic projection with the original color in proportion to severity.

A worked example: pure red (#FF0000) under deuteranopia simulates to roughly #9B7C00 — a muddy yellow-green. Pure green (#00FF00) becomes #DDDD2D, a similar olive shade. The two stop being distinguishable, which is exactly the perceptual problem deuteranopes report. A traffic-light icon set using only red and green for status loses its meaning; adding shape (circle vs. triangle) or position (top vs. bottom) restores it.

Limitations: simulation is not perception. The transforms model the central case of each deficiency in normal viewing conditions, but real color vision varies by individual severity, ambient lighting, and adaptation state. Anomalous trichromats — by far the largest group — see colors closer to normal than the dichromatic simulation suggests. The output is directional; treat it as a sanity check, not a clinical readout. The simulator also assumes sRGB input; wide-gamut images (Display P3, Rec. 2020) are clipped before transformation and may simulate slightly off.