For all gtk:
GNOME, Xfce, LXDE, and all OpenBox based.
This is a simple color scheme in one gtk file (gtkrc).
How to "install"
1. Create copy in your home folder
cp ~/Downloads/gtkrc ~/.themes/D1-Gray/gtk-2.0/gtkrc
(If file is in home folder "Downloads")
2. Apply theme "D1-Gray"
GNOME - System > Preferences > Appearance
Xfce - Menu > Settings > Appearance > Window (Apply)