Why Check Color Blindness Safety?
Two colors that look clearly different to most designers can appear nearly identical to someone with red-green color blindness — a trait affecting roughly 8% of men. This calculator lets you pick two colors and scores both a standard contrast ratio and a color-blindness-simulated distinguishability score.
How It's Calculated
Standard lightness contrast is computed with the WCAG formula, while each color is also run through transformation matrices modeling protanopia and deuteranopia perception. The closer the two simulated colors end up in RGB space, the harder they are to tell apart in practice.
Improving a Low Safety Score
A distance under 50 is flagged unsafe, 50-120 is caution, and 120+ is safe. If a pairing comes back unsafe, it's often easier in practice to widen the lightness gap or add non-color cues — icons, patterns, or text labels on charts and buttons — than to redesign the whole palette.
Frequently Asked Questions
Each color is transformed using matrices that model protanopia and deuteranopia perception, then the distance between the two transformed colors estimates how distinguishable they really are.
If you can't change the colors, increase the lightness contrast between them, or add non-color cues like icons, patterns, or text labels.