I'm using a template that came with an earlier version of InDesign and using it as a base for my document - I don't seem to be able to work out how to change the background colour (in this case, blue), to my desired colour. Explanatory screenshot is attached.
The background may be locked. In earlier versions of ID, locked objects could still be selected so it was common to lock things to keep them fom moving. With the new Layers Panel introduction in CS5 locked objects are no longer selectable by default, wich makes working with old templates a bit of a hassle. Fortunately, the Engineers added a preference item to allow you to be able to select locked objects, which returns behavior to what you expect from CS4 or earlier, or you can open the Layers panel, find the object in the stack, and unlock it.
There's also a reasonable chance that blue frame is on a master page, and that would be the place to change it. Looks to me like it needs to have some bleed added, too.