Summary

There's a private method that validates color input. This method is designed for scaler key value pairs, for example _check_color_like(color='green', gapcolor='orange')

I think this validation should be extended to list like input, something like _check_color_like(color=['green', 'orange', 'yellow']) or a second private function _check_color_like_listlike(**kwargs) that supports that input.

Proposed fix

The trickiest part of the coding is probably in sorting out how to recognize RGBA tuples as a color and not a list. And that might be partially solved by making a second function that always calls the list version -> this requires looking through the code for uses of color (hint: look for to_rgba) and checking if the type is ambiguous at the conversion stage. (For example in pie and bar, the colors could be either but are shoved into a generator and could be validated using _check_color_like as part of that loop iteration).

This was motivated by #24849 to be consistent with color checking in #23208

It's a good first issue because it's private API around printing a good error message and is not touching the public 'is_color_like' method. But, I will also accept if the solution is always use the singular case and wrap it in list comprehensions as needed.