Check the WCAG contrast ratio between a text color and its background, and see exactly which AA / AAA levels it passes.
Large headings, body copy, and the small print all need to clear the bar. This paragraph is regular body text at 16px — the size most of your readers actually see.
Small caption text · 12px · the hardest case to pass.
WCAG measures contrast as a ratio from 1:1 (identical) to 21:1 (black on white). Body text should hit 4.5:1 for AA and 7:1 for AAA. Large text (18px bold or 24px regular) and non-text UI elements only need 3:1.