I've finally managed to get relative CSS colors documentation published on MDN. This was a complex beast to tackle, and I'm proud to see it out! Get started at https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_colors/Relative_colors; also see the color function pages to find out what relative colors look like in each.
@chrisdavidmills I'm afraid at the last minute it's going to come out of my talk because I think I may have found a bug!
Seems like doing say hsl(from Canvas 30 s l); doesn't follow how Canvas (a system color) flips between near-white to near-black when color-scheme changes from light to dark.