Top bar system tray looks weird

Hey!

I'm new to Ubuntu MATE (I've used other distros, especially Manjaro, Kubuntu, and Elementary) and I love it so far. However, there's one issue I can't figure out. With my GTK theme, McMojave, the system tray background has a weird color. Is there a way in the GTK theme to take the panel from a different theme eg. Redmond and replace it? What part of the GTK theme manages the panel? If anyone knows the answer it would be very much appreciated. Thanks!

Can you try to set a custom color to the panel background and see if that works?

That didn't work for the GTK theme, but I found a different fix that worked perfectly (a line of code in ~/.config/gtk-3.0/gtk.css). Thanks though, I really appreciate the suggestion.