Openbox theme created to fit in nicely with the Arc GTK theme. Contributions are more than welcome, since it's far from perfect.
The original Arc theme for which it was made: https://github.com/horst3180/Arc-theme
Arc-Darker created by Narrat.
Under "Theme" click on "Install a new theme..." and point it to the .obt files.
Place the Arc and Arc-Dark directories either in ~/.themes (available for your user only) or in /usr/share/themes (available system wide).
It's available in the AUR.