Partially undo changes from 629d01eee0bf3c59c69b1b2798198955ee114b10
Partially undo changes from 629d01eee0bf3c59c69b1b2798198955ee114b10

I didn't notice that ´Widget#SetColor`can't just delegate to `Wisget#OverrideBackgroundColor`, therefore ´Widget#SetColor´ now uses it's original implementation.
gotk3/gotk3,gotk3/gotk3