The Mate environment is run by Gtk+. Gtk+ allows most elements in your desktop to be themed to the look you want. The Gtk+ Theme Selector lets you select the theme to use. The top of the Gtk+ Theme Selector has a list of installed themes. Simply click on a theme and your changes will be made. You can interactively demo all the widgets available in your selected theme in the lower half of the window. To add a theme to use: Click the Install new theme button. Navigate to the directory your theme is installed in. Open the gtkrc file which contains the specifications of your theme.