Created attachment 2852 dark window and light xfwm xfwm should inherit the color from his managed window see screenshot
That's how the theme is designed, definitely not a bug in xfwm4.
ok, and how can i do this? for example i want different colors only on some widgets/apps, maybe thunar in default grey(with a grey titlebar and black text) and xfburn in black(with a black titlebar and white text) btw im using a default xfwm-theme(Default-4.2)
You cannot, it's not how it works. The window manager i one gtk app just like others, there is not a widget per application.