So why, after all these countless millenia that the Green Lanterns have existed, have all these different colored rings and batteries cropped up within a couple of years? Especially ones with dubiously linked emotions. I mean greed? Really?
Yellow made a lot of sense overall, sure, but all these others? I realize there was a split by the Guardians and there's apparently some chick Guardians out there, but why now? And why so many goofy concepts? I mean seriously, this greed one is just baffling me alone.
And if the Guardians were so uber-powerful as to create the universe's most uber-powerful weapon, why are these solo renegade types able to do the same and become a viable threat?
Good questions all.
According to Geoff Johns' explanation - Most of it stems from the history of the corps. eg. A long time back there was split with some of the Blueskins leaving to become Zamorans and the "Guardians" for the star sapphire etc. The Red stem from the the previous version of the Green Lanterns (the Manhunters) getting a glitch and committing a massacre in sector 666. Then there are the psions of Vega (or something) that the Guardians have had a no-intrusion pact with (which of course gets broken multiple times) and they both hate each other. And all the colors are supposed to "represent emotions" (Love - Violet, Yellow- Fear, Hope - Blue, Indigo - Compassion (I don't know who's supposed to be their guardian) and so on). The weak point of course is that the original Lantern color of green (will-power) is not an emotion by itself.
So, the Violet color has an old off-shoot from the Oans as their guardian, the Blue color has a couple of guardians themselves (Ganthet and Sayd) who've left Oa to form their own corps and so on...