Simulate the common forms of color vision deficiency on a palette or on a screenshot. For a palette it also flags any two colors that are easy to tell apart normally and nearly identical to some learners, which is exactly what breaks a red and green right-and-wrong indicator.
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| Vision | #D22B2B | #2BA84A | #E8B400 | #2B6CD2 |
|---|---|---|---|---|
| Normal vision | ||||
| Deuteranopiaabout 1 in 16 men | ||||
| Protanopiaabout 1 in 100 men | ||||
| Tritanopiarare, and not sex-linked | ||||
| Achromatopsiavery rare |
These are distinct to most people and nearly identical to some. If either color is carrying meaning on its own, that meaning is lost. Add a shape, an icon or a label so the color is not the only signal.
Simulates deuteranopia, protanopia, tritanopia and complete color blindness, either on a palette or on a screenshot. For a palette it also compares every pair and flags any two colors that are easy to tell apart normally and nearly identical under one of the simulations.
Seeing a slide in simulated colors is interesting. Knowing that your correct green and your incorrect red become the same color for roughly one man in sixteen is actionable. If a color is the only thing carrying a meaning, that meaning disappears for those learners, and the fix is to add a shape, an icon or a word rather than to change the color.
The simulation uses the matrices from Machado, Oliveira and Fernandes, which is the model most accessibility tooling is built on. They are defined against linear light, so the colors are linearized before the matrix is applied and re-encoded afterwards. A lot of implementations skip that step and apply the matrix straight to the encoded values, which looks approximately right and is wrong by most in the mid-tones, which is exactly where course palettes sit.
It simulates the absence of a cone type, which is the severe form. Anomalous trichromacy, where a cone is shifted rather than missing, is far more common and milder. Treat a pass here as necessary rather than sufficient, and treat a failure as definite.