# Colour-Blindness Simulator See how your palette or screenshots look to the roughly 1 in 12 men and 1 in 200 women with colour vision deficiency. Built on the Machado (2009) model, applied in linear-light space. - #25D366&#FF6464collapse under deuteranopia (ΔE 5.6) Drop an image here, or **click to browse**. Screenshots of your UI work best. ## The types of colour vision deficiency **Protanopia** (no working red cones, ~1% of men) and **deuteranopia** (no working green cones, ~1% of men) both cause red–green confusion — the most common form. **Deuteranomaly**, a milder green-weakness, is the single most common type overall, affecting around 5% of men. **Tritanopia** (no working blue cones) is rare — under 0.01% — and causes blue–yellow confusion. **Achromatopsia**, total colour blindness, is rarer still and renders the world in shades of grey. Because red–green deficiency is by far the most prevalent, it's the case worth designing around first. ### Why a palette can pass contrast and still fail The contrast checker tells you whether text is legible against its background. It says nothing about whether two *different* colours can be told apart. A status system that uses red for "error" and green for "success" may have perfect text contrast and still be unreadable to someone with deuteranopia, because the two states collapse to nearly the same colour. That's what the confusion report above checks: it transforms every pair of your colours through each deficiency and flags pairs whose perceptual distance (ΔE) drops below the threshold where most people can reliably distinguish them. ### How the simulation works This tool uses the transformation matrices from Machado, Oliveira & Fernandes (2009), the model most accessibility tools rely on. Crucially, the matrices are applied in *linear-light* RGB — each colour is converted from gamma-encoded sRGB to linear, transformed, then converted back. Skipping that linearisation (as some quick CSS-filter approximations do) produces visibly wrong results, especially in saturated colours. Simulation is an approximation, not a lived experience — colour perception varies between individuals even with the same diagnosis. Treat the output as a strong directional signal: if a pairing collapses here, it will cause real problems. The fix is almost always the same — don't rely on hue alone. Add a second channel: an icon, a label, a pattern, a position, or a difference in lightness. ## Accessibility ### Screen reader support --- *Source: [ocxly.com/color-blindness-simulator.html](https://ocxly.com/color-blindness-simulator.html) — OCXLY, free 100% client-side privacy-first tools. A free colour-blindness simulator. See how your palette or screenshots look to people with protanopia, deuteranopia, tritanopia, and achromatopsia — using scientifically-accurate transforms. From OCXLY Dev.*