Currently (a part of) the category tree looks like this:
...
I think Category:Black allies and similar are kinda useless: The only thing they contain are the two subcategories of (primary/secondary) colored characters. So there are only useful if someone actually uses a subcategories.
In that case, since there are only 10 subcategories, wouldn't it be easier to get rid of that level and just put in the subcategories directly? Therefore I propose to change the category tree to:
...
(The other alternative I see would be to actually put articles inside Category:Black allies, most likely all characters with either that primary or secondary category. But I'm not sure whether is it worth to add 2 additional categories to nearly all characters.)