In the "Themes" dropdown menu, there's no "Default" option for it to follow Plasma's current color scheme (like in other apps such as Kdenlive and KDevelop). Custom created color themes are also not available to be picked in the menu. KDE Plasma Version: 5.18.5 KDE Frameworks Version: 5.70.0 Qt Version: 5.15.0
That is intentional: we don't want other styles than the ones we know work be shown in that menu because most of them are broken. If you really want Krita to run with another style, then set the following environment variable: KRITA_NO_STYLE_OVERRIDE=true And Krita will not override the system style.
That's true, but it's still not possible for Krita to follow Plasma's color scheme by default, or select it all if it happens to be a custom one.