Created attachment 149884 [details]
vid showing the bug in action, (excuse the blurriness, sub 100% scaling be doing that))

SUMMARY
When using "Tint all colours with accent colour" and picking the accent colour from the current wallpaper, the header lags behind a colourscheme as the wallpaper updates
e.g. current wall is red, you set the scheme, all's good, you update the wall to blue, the header is still red, update the wall to pink, the header only now turns blue

STEPS TO REPRODUCE
1. Enable "Tint all colours with accent colour" for a colourscheme and apply it
2. Use accent colour from current wallpaper
3. change the wallpaper cycling between a couple with very different dominant colours

OBSERVED RESULT
the header is always 1 colour behind

EXPECTED RESULT
header should update together with everything else

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux
(available in About System)
KDE Plasma Version: 5.25.0
KDE Frameworks Version: 5.59
Qt Version: 5.15.4

ADDITIONAL INFORMATION