@nocturneroadkill You can install theme files that were made by someone else and many people here have made them and shared them.
They are ‘human readable’ and fairly ‘human understandable’ so you can edit them to make your own colour theme if you like.
You put them in the krita resources folder in the colour-schemes folder then start krita and they will be available for selection.
Try these topics:
Topics tagged themes
Zoldyako's Themes for Krita v2 (recommended)