Problem

Since #24619 pcolormesh can handle RGB(A) arrays. There is an entirely reasonable request in Cartopy that pcolormesh there also supports this (SciTools/cartopy#2156). However, Cartopy’s wrapping logic for pcolormesh actually uses pcolor under the hood, so we’d need RGB(A) support in pcolor before we could get it working.

Proposed solution

I think we first need #25027 and then add RGB(A) logic on top of that, but I have not dug too far into the details.

cc @greglucas