Post color variable by Category or Author on main page?

Is there a way to make the post color dependent on the category? It seems like there would be, since the post color selection menu is under a tab titled “category” but I can’t see how to make the color variable by category name.

What I’m actually trying to do is make the post color on the main page variable by AUTHOR, but I haven’t found a way to do that and I think I can do a workaround with the Author Category plug-in if I have the capability to make post color variable by category.

Thanks for any help.