#FF0000: pure red color codes, contrast and shades

Red is where the two contrast methods split. WCAG 2 scores black text 5.25:1 and white text 4.00:1, so white passes only for large text: 24px and up, or about 18.66px bold. APCA, a newer method that isn't part of any WCAG standard, prefers white, at Lc -69.6 against Lc 40.0 for black.

The same number applies to red text on a white page. Error messages in pure red score 4.00:1 and fail AA for normal text. One step down the scale, #DB0000 still reads as a strong red and passes at 5.23:1.

Red and green are the pair people with the most common kinds of color blindness mix up. Pair a red error state with an icon or a word so it doesn't rely on color alone.

Use #FF0000 for large alerts, icons, badges and fills with black text. For error text and buttons with white labels, switch to #DB0000.

The lighter steps lose contrast against white fast, so keep them for backgrounds like error banners, with dark text on top. Click a shade to open it in the Color Picker.