Created attachment 136012 [details]
example of breeze dark colorscheme activetitlebar not updating

SUMMARY
Active Titlebar color is not updated for the Breeze Dark color scheme, both in Preview or on active Window. Works OK for Breeze color scheme.

When using System Settings>Appearance>Colors, selecting Breeze Dark color scheme 
then editing it and changing Common Colors>Active Titlebar

STEPS TO REPRODUCE
1. System Settings > Appearance > Colors
2. Click the Pen button on Breeze Dark, for Edit Color Scheme
3. Change Common Colors > Active Titlebar color
4. Save as > Breeze Dark2
5. Choose saved Breeze Dark2 color scheme as active, Apply

OBSERVED RESULT
Active Titlebar color is default color, both in Color Scheme preview and on the active window.

EXPECTED RESULT
Active Titlebar color is selected color for custom color scheme, both in Color Scheme preview and on the active window.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20210217
KDE Plasma Version: 5.21.0
KDE Frameworks Version: 5.79.0
Qt Version: 5.15.2
Kernel Version: 5.10.16-1-default
OS Type: 64-bit
Graphics Platform: X11
NVIDIA driver: 460.39
ADDITIONAL INFORMATION
Attached screenshot:
Green rectangle shows correct working behavior for Breeze color scheme, Active Titlebar color is updated in preview.
Red rectangle shows color not updated in Titlebar or preview.
Tested with KDE Neon neon-user-20210218-0944.iso also.