The colours mainly depend on what element the solar particles are hitting - so Greenish-red if they hit Oxygen (Most common) and Red with occasional Blue (Blue is rarest) if they hit Nitrogen. I think both are predominantly green, with red possibly being slightly more common in the Aurora Australis. I think just have 'Aurora' as one, but like the Great Barrier reef have the chance for two on either pole. Otherwise you could have the Aurora Australis in the north or vice versa.
Well, I was under the impression that the Australis was more red-green, and Borealis more blue-green, but the Barrier Reef idea would work better.