What it is
Normal text needs at least 4.5:1 contrast and large text at least 3:1 under WCAG AA. Information conveyed by color also needs a text, icon, pattern, or positional cue.
Why it matters
Low-contrast copy becomes unreadable for many recipients and can fail completely when a client changes colors for dark mode.
How to implement
Measure actual foreground and background pairs, including buttons and fallback colors. Underline links in body copy and label states such as errors or success in words.
Common mistakes
- Testing brand swatches but not rendered combinations.
- Assuming bold text qualifies as large text.
- Distinguishing links from copy only by color.
Verification
Measure every text style and inspect forced dark mode in major clients. Check the message in grayscale to expose color-only distinctions.