See any of the pages under General on the Curriculum page - they all use the standard "SSE" theme combo.
Editing the following templates will potentially affect a lot of pages:
Template:Box themes combo - the themes (sandy, gaia, ...) associated with the various box types (nav, intro, preparation, tips, ...) in a particular page's theme combo (mix, sse, ...).
Template:Box Theme Attribute - specifies the attributes (border colour, foreground text colour, title text colour, title background colour, etc.) associated with each theme (blues, gaia, sandy, ...).
Template:Theme box image - specifies combinations of images associated with page theme combos (e.g. mix, sse, etc.).
Template:Module Page Image - images associated with (typically) a box type (e.g. navigator, orientation, tips, ...).
