Colour Blindness Simulator
See how your image or design looks to someone with a colour vision deficiency.
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Roughly one man in twelve sees colour differently
Colour vision deficiency affects around 8% of men and 0.5% of women. The most common forms weaken or remove the ability to distinguish red from green, which is precisely the pairing designers reach for to mean "error" and "success". This tool renders your image through simulations of the three main types so you can see what actually reaches those viewers.
What to do about it
The fix is rarely to change the colours. It is to stop relying on colour as the only signal: add an icon beside a status, a label on a chart line, an underline on a link. If your design still makes sense in the deuteranopia panel, it will make sense to almost everyone.
Frequently asked questions
How accurate is the simulation?
It uses the standard published transformation matrices, which model the common inherited forms well. Individual experience varies, so treat it as a design check rather than a medical tool.
Which type should I design for?
Deuteranopia is by far the most common, so start there. If a design survives it and still has non-colour cues, the other types are rarely a problem.