I know how to change the file colors in Appearance & Behavior, but how can I change the background color of the active tab? It's probably somewhere in the theme section, but how do I change that?
unfortunately it's not customizable. Please vote for IDEA-126775 to increase its priority and be notified about updates.
Please also check this thread: https://devnet.jetbrains.com/message/5532304#5532304 - you might find the suggestions helpful