SUMMARY As title I updated my system this morning and rebooted. After I got into the desktop session, I noticed that one of my applications' tray icon in the panel become colorless, which is colored in plasma 6.2.5 STEPS TO REPRODUCE 1. Login into desktop session OBSERVED RESULT The tray icon is colorless. EXPECTED RESULT The tray icon is colorful SOFTWARE/OS VERSIONS Operating System: Arch Linux KDE Plasma Version: 6.3.0 KDE Frameworks Version: 6.10.0 Qt Version: 6.8.2 Kernel Version: 6.6.72-x64v3-xanmod1-1-lts (64-bit) Graphics Platform: Wayland Processors: 16 × AMD Ryzen 7 5800H with Radeon Graphics Memory: 13.5 GiB of RAM Graphics Processor: AMD Radeon Graphics ADDITIONAL INFORMATION This is the program that corresponds to the tray icon: https://github.com/pwr-Solaar/Solaar Here is the screenshot: https://sm.ms/image/hmBtMaVTcXlvkwU The tray icon in red square is the one that has problem. Here is a screen record from September last year: https://vimeo.com/1014038156?share=copy You can notice that the tray icon has color that time.
It is likely using a symbolic icon in the system tray, which is expected behavior. If symbolic icon is present, the system tray will always prefer that over the colored one. Some applications let you change the color of the system tray icon.
Your explanation doesn't account for the fact that the tray icon is colored in Plasma 6.2.x. If the tray icon will always prefer the symbolic one over the colored one, the tray icon should be colorless in Plasma 6.2.x too.
The added code to prefer symbolic icons was introduced in Plasma 6.3, which is why it changed for you after you upgraded to Plasma 6.3. As such, I'm afraid this is considered intentional.