I'm not much into customization but recently I've found this cool theme that I really like, and as we approach the end of the year things have been slow and a bit boring, so I took the time to spice things up a bit.
I even created a simple firefox theme for it!
What I haven't yet figured out is how to get rid of the apple-style action buttons. It also doesn't apply the theme on every program, for example GIMP or KeePassXC.