Focus indicators also have to be large enough to be noticeable, covering at least a 2-pixel-thick border around the element. And for error messages, readability is even more critical, with text requiring a 4.5:1 contrast ratio to stand out clearly.

But here’s the catch: WCAG currently relies on a luminance-based formula that doesn’t always reflect how humans perceive contrast in the real world. It underweights blue, struggles with certain hues, and doesn’t account for ambient light or screen quality. That’s why WCAG 3 is moving toward APCA (Advanced Perceptual Contrast Algorithm), a new model designed to match human perception more closely.

The safest choice? High contrast, like black on white. Classic, timeless, and easy to read. But be careful: pure black (#000000) on pure white (#FFFFFF) can be too harsh, especially for users with dyslexia or light sensitivity. WCAG doesn’t flag it, but accessibility experts advise against it. A slightly softer black or off-white often reads better without losing contrast.

But if black and white doesn’t suit your design, that’s fine. Just use contrast-checking tools to confirm that your color combinations meet accessibility guidelines, or provide a high-contrast mode as an alternative for those who need it.

And remember. Regardless of the colors you choose, keep them consistent. Predictable color schemes make navigation easier, especially for users with cognitive disabilities.

Choosing colors with enough contrast is about making deliberate choices that enhance clarity without sacrificing aesthetics. After all, even the most beautifully designed interface fails if users can’t read a button or find what they need.

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