Linux Mate Desktop Volume OSD style

Volume On screen Display (OSD) using silly colours?
Create this file ~/.config/gtk-3.0/gtk.css
containing:

I have michael-hi to thank for this gem. From the Linux Mint forum Tue Jan 21, 2025 7:50 am
https://forums.linuxmint.com/viewtopic.php?p=2579804#p2579804