Color Blindness

Color blindness is a difference in color vision that makes some hues difficult or impossible to tell apart, especially when an interface uses red and green as opposites.

A status dashboard can look obvious to its designer: green dot means passed, red dot means failed. Through another pair of eyes, both dots may become the same muddy color. If color is the only thing carrying the message, the message can disappear.

The fix is not finding one magical pair of safe colors. Add another channel: a check and an x, different shapes, or the words Passed and Failed. The colors can stay and still do useful work, but nobody has to depend on them alone.

You'll hear colorblind, color vision deficiency, red-green color blindness, colorblind safe, and color alone. Contrast is a different problem. Contrast asks whether an element separates from its background; color blindness asks whether two hues separate from each other.

Design the status so it survives in grayscale. That quick test catches a surprising number of failures. Color should reinforce meaning, not be the only place meaning lives.