Themes apply to the title bar of Openspace and to the gadget windows. Selecting different themes for different gadgets is a useful way of distinguishing between them.
Procedure
Click the gadget whose theme you want to change:
.
Click the gadget to display the User Preferences area.
From the Themes Gallery, select the theme you want to use.
The gadget is automatically updated to use the new theme.
Repeat these steps for each gadget whose theme you want to change.