Created attachment 97278 [details] Screenshot of the system tray. Icons with purple background. Some icons have a purple background. Applications such as the official telegram desktop client and the qt5 branch of kfilebox. I don't know if its relevant but both were installed from Arch AUR.
My Telegram tray icon shows this behaviour already for several months from time to time. Hadn't time to look into it but maybe now is the time. This bug seems to be related: https://bugs.kde.org/show_bug.cgi?id=356937
It seems like the same bug. can you tell me (in the other bug) which telegram app you were using (there appear to be a few) *** This bug has been marked as a duplicate of bug 356937 ***