I posted about this some time ago at Forrst, but it's worth to mention again.
UIColor can be also a pattern and there are some predefined styles like linen from multitasking.

Try this:

// Dark
self.view.backgroundColor = [UIColor viewFlipsideBackgroundColor];
// Light
self.view.backgroundColor = [UIColor underPageBackgroundColor];

You can check other default patterns at iPhone Development Wiki.