UX Design
Color-Only State
A color-only state is when an interface uses color as the single signal for meaning, such as a field turning red to indicate an error. Anyone who cannot perceive that color difference misses the message entirely.
Why it matters
Color blindness is common, and color can also be washed out by bright sunlight or low-quality screens. Relying on color alone quietly excludes people and leaves them confused about what went wrong.
In depth
The fix is to always pair color with a second cue — an icon, text, a shape, or an underline — so the meaning survives without it. This is a core WCAG requirement, which states that color must never be the only means of conveying information. A good test is to imagine the screen in grayscale: if a state disappears, it was relying on color alone.
Real-world example
An error shown only by a red border is invisible to many colorblind users; adding an icon and a short message like "Email is required" makes the problem clear to everyone.
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