There was some discussion from JJJ, who said it is difficult for a plugin developer to maintain consistency across versions, if they happen to add something in the admin that uses colors. I think his example was for event calendars.
The work they are doing is coming in stages: there was some a11y changes, then they did the color palette consolidation, and are still working on making the whole thing use CSS custom properties.
I was interested in getting the custom properties, but I don’t like the approach they are using. I think the colors should be consolidated even more, and use different properties like background gradients and box shadows with semi-transparent black and white to indicate state (disabled, active, focus, hover) instead of specifying a different color.
There is an audit report that we can use, to check how many colors (and other things) are used. There’s a link to the repo at the top: CSS Audit for wp-admin
I was hoping to make color changes to the admin, to distinguish CP from WP, but I suppose changing various shades of gray to make more contrast is a good thing, regardless.