Ok, that sounds like there is no 'general' way to change background/foreground settings for QWidgets when QPalette's influence varies so much, right?
That's too bad...

But were my speculations about the way of using QPalette right (first post)? Did I understand that stuff correctly? In principle, would it work to set the QWidget's background color to the same background color as grey windows by setting backgroundRole to QPalette::Window (if OS would allow it) ? Or did I understand the whole stuff fundamentally wrong?