Hope it's okay to ask about themes here... It's actually more problematic than it looks!
In my bottom panel, it's very hard to tell visually if one of the pinned applications is currently running or not. In the screenshot, Firefox is running in the foreground, indicate by that thin grey stripe at the bottom. Spotify beside it is running in the background, and the only way you can tell is that even paler gray stripe, with barely any contrast to its background.
What would you recommend to make that more clearly visible - short of choosing a different theme (because that will also change a bunch of other stuff that I like the way it is).