In category settings, I see the message “You can’t select colors because you have a category style of none.” However, it’s used by the Category Icons theme component, and that works quite nicely with “none” as the style.
My current work-around is to change the style setting, quickly set the category color, and quickly set it back. But that’s kind of silly. Please just allow it to be set (maybe with a note that it won’t change the color unless a theme does something with it, instead of hiding the setting). Thanks!