category colors change even if "Use custom color" is unchecked.

Even if you don't have the color option checked for categories & forums it still utilizes the color choice.

Also, since this has been implemented all themes basically break (probably due to this bug) using a black background for categories & the like.

Just thought i'd bring this to your attention as a potential bug. :)

I think I’ll need to remove the default value. It’s probably overwriting. But if you’d remove the value in the color box, you’ll be able to save without color. I’ll add this to the list though.

Can you also add an option within the theme settings to completely disable/overwrite the color for categories & forums for a specific theme so that theme doesn't use them even if they're set? Would this be possible?

I’m not sure if I’m able to make this theme-aware. I’m feel like this would overcomplicate things. But I’ll see what I can do.