There are plenty of things in the EU about where/how the Death Star was constructed. But going solely by the movies, we really have no idea. So I suggest going for something that looks cool but doesn't confuse.
Blue looks good, but it is too much like Alderaan.
Yellow/tan is too much like Tatooine.
Red is too much like Yavin.
But red with a ring (Geonosis) is visually different enough so as not be confuse the viewer. For those with a keen eye, this would easily be identified as Geonosis, which is one possible location for the Death Star's construction. Plus, I think it would be REALLY COOL to see a red ringed planet in this shot.