CSS templates are designs that use CSS (Cascading StyleSheets) not only for general formatting and styling, but also for positioning and sizing all page elements. This should take you to the Overview section of the Gantry Admin for that theme. This can include color-coded presets, fonts, accent colors and colors for specific portions of the page, as well as custom elements such as colors, block styles, and backgrounds. For example, if you have an outline set up that you would like to apply specifically to your About page, you can do so here. All variations are organized separately so you can use / customize the template very easily.