this might be able to be taken care of in budgie-desktop-settings
(right click your desktop).
make sure your widgets/icon combo is dark. toggle built-in theme and toggle dark-theme sliders. play around with them.
black backgrounds and light titlebars I've taken care of this way.
I throw everything at the problem til its fixed and I don't write stuff down (my bad) so sorry for all the babble. edit/sp