1.4.11 Non-Text Contrast
Make sure you read the entire fucking Understanding document, because this criterion is confusing as hell. Important visual stuff that isn't text should have at least 3:1 contrast against the less important stuff it's next to.
What's important? Fuck if anyone knows. People have debated about it for over a year. Meaningful graphics and the existence of interactive controls, I guess. Maybe states? Probably not states.
Fuck WCAG, talk to users.