It turns out there aren't just Green Lanterns any more. Instead, there's a complete rainbow of Lanterns, each powered by a different "emotion".
So there are Red Lanterns powered by rage, and an Orange Lantern powered by... envy, I think? And the Yellow Lanterns, a.k.a. the Sinestro Corps, are powered by fear. Or rather, by their ability to instill fear in others. It's not completely clear to me how it's supposed to work, really. There are good rainbow lantern colours too. The Blue "Hope" Lanterns apparently super-charge Green Lanterns' rings (Green Lanterns are powered by Will, by the way). And yes, there are Indigo and Violet lanterns too.
In the current Blackest Night storyline, it turns out there are Black Lanterns as well. And the Black Lanterns are all people who've been raised by the dead. Mostly superheroes who've been killed off recently in other Event Comics. And they've been killing off a number of other heroes just so that they can turn them into Black Lanterns and give them nifty costumes.
As soon as I heard about this storyline, it was obvious to me how it was going to turn out. After many dramatic and heroic battles, the multitude of rainbow-coloured lanterns will come together and fuse their rings' powers into one beam of white light. Because white is made up of all of the colours of light. They'll probably have to trick the bad-guy lantern colours into participating somehow. Or they'll decide the black lanterns are a bigger threat, or something.
And while I'm at it, I'm going to go on record predicting that if the White Lantern Light has a humanoid form, it'll be female, and she won't have any clothes. She'll be all glowy white light so you won't be able to tell if she's naked or not, though.
Anyway. I wrote a little theme song for the inevitable White Lantern Corps.
And now I'm going to share it with you.
There's music, too, but I'll spare you that part for now.
The White Lantern Theme Song
All of the Lanterns of the rainbow
Working together in harmonyyyyy
When we unite, we shine the white light
And bring peace ever closer for you and meeeeee...
It needs another couple of verses, really. Anybody want to contribute?