Numix is a modern flat theme with a combination of light and dark elements. It supports Gnome, Unity, XFCE and Openbox.
Numix is a part of the Numix Project.
Extract the zip file to the themes directory i.e.
To set the theme in Gnome, run the following commands in Terminal,
gsettings set org.gnome.desktop.interface gtk-theme "Numix" gsettings set org.gnome.desktop.wm.preferences theme "Numix"
To set the theme in Xfce, run the following commands in Terminal,
xfconf-query -c xsettings -p /Net/ThemeName -s "Numix" xfconf-query -c xfwm4 -p /general/theme -s "Numix"
GTK+ 3.6 or above
Murrine theme engine
Report bugs or contribute at GitHub