SUMMARY & TO REPRODUCE Kate provides two ways to change editor's theme (Or at least these two ways): 1. From top menu "Settings > Editor Color Theme > {THEME}" 2. From top menu "Settings > Configure Kate..." then from left menu "Color theme > Default Theme > {THEME}" The FIRST and SECOND methods overlap each other if they are used SUBSEQUENTLY. i.e If you change the theme using the FIRST method and then using the SECOND one subsequently (without re-opening Kate); the result will be a mixture of those two themes! SYSTEM Operating System: Arch Linux KDE Plasma Version: 6.2.4 KDE Frameworks Version: 6.8.0 Qt Version: 6.8.1 Kernel Version: 6.12.3-arch1-1 (64-bit) Graphics Platform: X11 Processors: 4 × Intel® Core™ i5-7200U CPU @ 2.50GHz Memory: 7.6 GiB of RAM Graphics Processor: Mesa Intel® HD Graphics 620
That is expected behavior, the first action will just change it for the current view and that has precedence over the global change you do afterwards.