Colour Blindness Simulator

What it's for

See a picture as people with colour blindness see it. Around 1 in 12 men and 1 in 200 women have some colour blindness, most often telling red from green. Charts, maps, status lights and “red means error” designs that rely on colour alone can lose their meaning.

For example, before publishing a dashboard whose lines are red and green, take a screenshot and check here that the lines can still be told apart.

How to use it

Choose a picture or screenshot, or drop or paste it on the page. Show picks every kind side by side, or one kind with the original:

• Protanopia and deuteranopia: no red or no green cones, the common red–green colour blindness.
• Tritanopia: no blue cones, which confuses blue with green and yellow with pink.
• Achromatopsia: no colour at all.

Severity blends towards normal vision for the milder forms most people have (protanomaly, deuteranomaly and tritanomaly). Each view has a Save button for a PNG. The choice of view is remembered in this browser.

Example

Take a screenshot of four blocks coloured red, green, blue and yellow, and choose it here with Every kind.

In the protanopia and deuteranopia views, the red and green blocks become similar olive browns and the yellow stays yellow; in achromatopsia all four are greys.

Good to know

It uses the Machado, Oliveira and Fernandes (2009) model, a good approximation; no simulation shows exactly what a given person sees. Severities below 100% blend the full simulation with the original, which is close to but not the same as the model’s own tables. Large pictures are scaled to 1,200 pixels across.