The idea (DS, shut your ears...it blew your mind last time!) is that the colours of the Spectrum represent emotions. Red = rage, Orange = avarice, Yellow = fear, Green = willpower, Blue = hope, Indigo = Compassion, Vilolet = love. Then white and black represent life and death respectively. So each set of lanterns bascially draw on some part of them that is transformed into power via the rings.
I rather like that idea so I don't mind how many Lantern Corps there are. As it's based on the Spectrum I don't see them brining in any beyond that now they have black and white.
Ultimately I love the idea of interglactic, superpowered 'knights' doing battle with one another. Batman has always been a fave, as have the X-Men. But I've really got into the noble alien/cosmic hero so I'm reading a lot of the stuff like Captain Marvel (the Marvel version), Green Lanterns and Nightwing/Firebird from the Superman mythos.
By the way, there's a great jokey bit in Dragon Age Orgins. You get various random encounters. One is a cuit scene where a meteor crashes down. As your party of adventurers walk past they come upon a man and woman, the latter being called Marta (Martha) who have found a baby boy in the crater! You can dig around in there yourself and get meteor ore. If you take it along to another part of the game you get a magic sword called Starfang that looks like the crystals from Superman...nice!!!