Created attachment 139289 [details]
Screenshot to show that the if dark theme is applied to Plasma desktop and the lines that are identical are in white color, it hurts our eyes.

SUMMARY
If dark theme is applied (like Breeze Dark), the identical lines of two comparing files show up in white color.

STEPS TO REPRODUCE
1. Make sure you have a dark theme (say Breeze Dark as Global Theme) applied to your KDE Plasma desktop.
2. Have a text file containing more lines (like 100 lines).
3. Duplicate the text file.
4. Open the duplicated text file and make changes to any one (or very few) line of it.
5. Compare the original and the duplicated files with Kompare.
6. Get your eyes hurt.

OBSERVED RESULT
In Settings > Configure Kompare... > View > Appearance, there are only 4 Colors to chose — Removed color, Changed color, Added color and Applied color — but there is no choice to change color for lines with no changes made, hence they show up in white color without respecting dark mode. This does not matter if the identical lines are very few and non-adjacent, but this hurts eyes if most of the lines (adjacent lines) are identical making it look as if there are two white pages.

EXPECTED RESULT
1. Color inversion should be done according to the dark theme applied, the same way how Kate application does. If the theme is a dark theme, the background color should also be dark (like what Kate has) and text color should be light.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma:
(available in About System)
KDE Plasma Version: 5.22.0
KDE Frameworks Version: 5.82.0
Qt Version: 5.15.2