Was just thinking this. Purple and teal are probably a better separation than red and green, though I don’t know for sure. In the past, I used salmon and teal, as I think the split is a bit clearer, and also more recognizable to folks with normal vision.
Like “mathematically” accessible? In my experience the WCAG tests are only useful as a starting point and guidelines. In reality there are many more factors like display hardware and preexisting notions of meaning. Like for instance purple is not a color I associate with “no” :-)
Is there a better color profile to convey Y/N semantics and address visual accessibility issues?