Designing accessible color systems and ensuring contrast across themes

[Why contrast still breaks at scale (WCAG fundamentals and common blind spots)] [How to structure color tokens so themes don't betray accessibility] [Practical test matrix: how to test contrast across themes, states, and components] [Developer handoff and CI: tokens, Storybook, and automated contrast checks] [A ready-to-run checklist and step-by-step protocol] Color contrast is the accessibility failure you'll still discover the day before release — not because WCAG is vague, but because the system around your colors is fragile. Treating palette values as static hex strings guarantees regressions when themes, overlays, or component states multiply. The previous release cycle illustrated the pattern: designers hand over a brand palette; engineers wire the hex values into components; QA flags a dozen contrast failures across hover, focus, and dark-mode states; designers push new swatches; the system ends up with local fixes and visual drift. That cascade costs time, creates inconsistent