For some reason you have no color or border shading on windows applications.

This is not related to TSplus itself.

This behavior is actually related to your system, and not TSplus.

By default, any application's window tittle bar is white, you will need to change this behavior using theses topics :

Tittle bar :

Borders and shadows :

If it is not working, then you will need to make sure that no local GPO is impacting this settings during your users sessions.