You can use These Tools to change theme: Gnome Tweak Tool, Ubuntu Tweak
There are three GTK2, GTK3, GNOME Shell and Cinnamon themes in all (Red, Green and Blue) as well as common Metacity/Mutter and XFWM themes for all three themes (Zukitwo-Primary-Colors).
To install Zukitwo-Primary-Colors theme on Ubuntu/Linux Mint (Press Ctrl+Alt+T) and copy the following commands in the Terminal:
Enjoy
- mkdir ~/.themes
- wget -O zukitwo_pc.zip http://dl.dropbox.com/u/53319850/NoobsLab.com/zukitwo_primary_colors.zip
- unzip zukitwo_pc.zip -d ~/.themes
Source: Deviantart