SUMMARY
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The option in color scheme settings to "Make window titlebars accent-colored" works rather inconsistently.
***

STEPS TO REPRODUCE
1. System Settings > Color
2. Edit a color scheme
3. Options > Make window titlebars accent-colored

OBSERVED RESULT
- In general, it doesn't work for the accent color from the current color scheme (I would expect Breeze Blue to be used for this option with the Breeze themes).
- For copies of Breeze Light and Breeze dark with the option enabled, it applies the color not only to the titlebar but also to the header.
- For Breeze Light and Breeze Dark, it applies a fainter version also to inactive windows, whereas for Breeze Classic, inactive windows keep their original background color.
- Whenever the the color is applied to the active window, it doesn't use the actual accent color, but some fainter version of it.

EXPECTED RESULT
- The accent color gets applied in its original version to the titlebar of the active window and possibly in a more finted version to inactive windows, and regardless of which accent color mode or which base color scheme is used.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux
KDE Plasma Version: 5.26.5
KDE Frameworks Version: 5.101.0
Qt Version: 5.15.8
Kernel Version: 6.1.5-arch2-1 (64-bit)
Graphics Platform: X11