About the Colour Blindness Simulator
Around one in twelve men and one in two hundred women have some form of colour vision deficiency; red-green types are by far the most common. That means a red/green status indicator, a multi-line chart distinguished only by hue, or a link marked purely by colour will fail for a meaningful slice of your audience. Simulating the effect is the fastest way to find those cases.
How to use the Colour Blindness Simulator
- Upload a screenshot, chart or design — or edit the six palette swatches.
- Compare the normal-vision panel with each simulation.
- Look for colours that merge into the same shade.
- Add a second cue — shape, label, pattern or position — wherever they do.
Why use this tool?
Six vision types
Protanopia, deuteranopia, tritanopia, achromatopsia and the milder protanomaly and deuteranomaly.
Images or palettes
Test a full screenshot, or just check whether your brand colours stay distinguishable.
Local processing
Images are handled by the browser with CSS filters and never uploaded.
Frequently asked questions
Which type is most common?
Deuteranomaly, a reduced sensitivity to green, followed by protanomaly. Full dichromacy such as deuteranopia is rarer but is the stricter test.
Is red-green the only problem pair?
No. Blue-yellow confusion (tritan types) is rarer but real, and low-saturation pastels of any hue can merge for everyone at small sizes.
How do I fix a failing chart?
Vary lightness as well as hue, add direct labels or patterns, and never rely on colour alone to convey meaning — that is WCAG success criterion 1.4.1.