I voted for the natural look too.
I think, even if (or maybe especially if!) you're going to go for more than one pair, you should stick to one morph and not mix; if they decide to interbreed and you've golds and electric blues, the fry would be neither and they'd probaby come out as, not very well marked or coloured, wild types anyway.
It's taken years of selective breeding to get those colours, it would be almost pointless to lose the genes.
I would have thought you would have plenty of space for two pairs; it's just that they wouldn't care which colour fish they're mating with, so the babies would be 'mongrels'.
As I said, it would almost certainly come out looking like a poorly marked and coloured wild anyway; most of these colour morphs are based on a recessive gene.