@CennoxX
A restartup should restore the correct color.
It’s due to the absence of style “Change History margin” in your stylers.xml:
https://github.com/notepad-plus-plus/notepad-plus-plus/blob/master/PowerEditor/src/stylers.model.xml#L1416
You can add it yourself into in your stylers.xml, or just remove it, a new stylers.xml will be copied from stylers.model.xml
The Change History margin’s color is difficult to manage.
It could use the Line Number margin’s color style ID 33 (Scintilla default behaviour) and users cannot customize its color at all.
Or we provide customization (it’s the current option) to disassociate it from style ID 33, but there will be such glitch while switching among the themes.
We have to choose one or another - the perfect world doesn’t exist.