My Color Combo Passes WCAG – So Why Does It Still Hurt to Look At?

- APCA does define a “maximum contrast” (currently set at Lc −90 for dark-mode text) to prevent extremes that actually hurt readability.

- But that limit exists purely to guard accessibility - i.e. ensure text remains legible - not to model all factors of visual comfort. APCA’s core goal is “readability contrast” not halation, ambient-light mismatch, or eye-fatigue.

So yes: what’s accessible (legible) often overlaps what’s comfortable, but it doesn’t guarantee it. The "Color Comfort Score" aims to pick up where APCA leaves off, by folding in those extra perceptual and environmental factors.

In fact, even at lower brightness, bright-on-dark can still cause halation, retinal fatigue, and visual vibration, especially in low-light environments.

Designing softer contrasts does the same thing, but more intentionally - and we can't assume users have ideal screen settings. Better to design for humans, not hardware.

Also: white-on-black is just one example.