A colour blindness simulator redraws colours the way people with a missing or weak cone type see them. Upload a screenshot or paste your palette to view it in eight vision types at once. The tool also flags colour pairs that look distinct to most people but merge for others, and suggests a lighter or darker replacement.
| Type | What changes | Commonly confused |
|---|---|---|
| Deuteranomaly and deuteranopia | Weak or missing green cones | Red and green, brown and green, blue and purple |
| Protanomaly and protanopia | Weak or missing red cones; reds look darker | Red and green, red and black |
| Tritanomaly and tritanopia | Weak or missing blue cones (rare) | Blue and green, yellow and pink |
| Achromatopsia | No working cones (very rare) | Everything except lightness |
Updated
Two ways in: drop a screenshot of a page, chart or design, or paste a list of hex colours. Every simulation runs in your browser, and nothing is uploaded.
The red and green cones in the eye respond to overlapping ranges of light. When one of them is missing or shifted, the brain loses most of the difference between reds, oranges, yellows and greens, and those colours line up along a single scale from dark to light.
That is why traffic-light status colours, red and green chart lines, and success or error badges are the usual problems. Keep the meaning in a word or icon and make the two colours differ in lightness.
Each colour is converted to OKLab, a colour space designed so that equal distances look roughly equally different. The tool measures the distance between every pair before and after simulation. A pair that is clearly different normally but falls below the threshold in a simulation is flagged.
The threshold is a judgement call for small flat areas such as chart lines, legend swatches and badges. Large blocks of colour are easier to tell apart, so a flagged pair may be fine as two full-width sections.
According to the US National Eye Institute, red-green colour blindness is the most common form, and it is far more common in men than in women. Among people of Northern European descent it affects up to about 1 in 12 men and 1 in 200 women. Blue-yellow types and complete colour blindness are rare.
It uses the Machado, Oliveira and Fernandes model, which is widely used and well regarded, with full strength for the -opia types and a moderate strength for the -anomaly types. Real people vary: two people with the same diagnosis can see somewhat differently, and screens and lighting change things too. Treat it as a strong guide, not a diagnosis.
Not from this page. Browsers do not let one site load and read another site's pixels. Take a screenshot of the page (on most systems Shift + Cmd + 4 on a Mac or Win + Shift + S on Windows) and drop it here instead.
Not entirely. Contrast checkers compare lightness between text and background, which does help everyone. But two chart colours or two status colours can each pass against white and still look the same to someone with deuteranopia. Check pairs of colours that must be told apart, which is what the palette check here does.
Related: Colour contrast checker, Accessible colour palette generator, Colour palette generator, Hex opacity calculator, Website accessibility checklist.
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