There are plugin that will change the appearance of the UI.
The simplest way to change the ‘cosmetic’ appearance, i.e. the colours, is to download and use a ‘theme’ file.
Please read this topic: Zoldyako's Themes for Krita v2
And this one: Krita themes - changing stuff
If you use the forum Search to look for ‘themes’ then you’ll find lots of topic on the subject, especially if you look in the Resources category:
Search results for 'theme #resources' - Krita Artists