Currently, Krita has no option to respect the KDE system color schemes but only provides its own. It should have a option to use the system default color scheme similar to other KDE apps like Kate, Konsole, Okular among others. As it is currently implemented, there is also a mismatch of the Krita accent color and the KDE accent color in the UI, with the latter appearing in some places like hovering over menus. This inconsistency doesn't exist in the other apps I mentioned when changing color scheme. Reporting as a minor bug because of this visual inconsistency.
As an artists' application, Krita is designed by artists to work best for artists, not to blend in with a desktop. Since blending in with the desktop is not a goal, I'm marking this as intentional.
Created attachment 154041 [details] comparison of kate and krita
Respectfully I think it should be provided as a option, since it is not mandatory in the other applications I mentioned to use the system color scheme, but it is possible to use a custom one. Other graphics applications like GIMP also let you use the system provided theme. I attached a comparison of Kate and Krita's current UI to select the in-app theme to better explain what I'm talking about, you can also see in this screenshot the visual bug where Krita applies two accent colors (one from the KDE system theme which is Breeze Light in this example and one from its own theme), whereas Kate applies the whole theme consistently in all its interface with only one accent color. This should be fixed regardless because it's a inconsistency that bothers specifically who is going to use their own color scheme.