Even if you've got a good handle on the admittedly complicated backstory to Blackest Night, that still leaves seven new Corps to keep track of. The colors themselves are actually fairly easy to remember, as they're the same as the colors of the rainbow. That's right - it's time to bust out the old ROY G BIV mnemonic, because it's pretty much the entire key to Blackest Night. Well, that and the black light of the Black Lantern Corps. That's probably important as well.
In an interview with Publisher's Weekly about a month ago, Geoff Johns provided one of his clearest explanations for the mechanics of the various colors. Each of the seven represents a different aspect of the emotional spectrum, something that sentient life created simply by existing.