Optimystic said:
I don't understand the differences between all the ring colors. All I know is the yellow one is evil (is it Cowardice? Greed? I forget) and the bad guy uses it. Beyond that, I don't know what it can do that the other colors can't, if all the colors have a special power etc.
Yellow represents fear, and it doesn't seem to discriminate between the forces of good and evil. The rings seek out those who can instill great fear, no more and no less. (Batman was offered a ring at one point, for example).
Red represents rage and has the notable ability of turning its users into animalistic beasts.
Orange represents avarice, or greed. Notable in that there aren't actually any Corpsmen of this spectrum; one creature holds both the orange power battery and the orange ring, and because he's too greedy to share, he creates the rest of the Orange Lantern Corps out of energy.
Blue represents hope, and can act as a direct opposite of red; for example, Blue Lanterns have the ability to extinguish the everlasting blasts of fire that Red Lanterns can create.
Indigo represents compassion. Because of their great emotional empathy, members of the Indigo Tribe can replicate the powers of other Corpsmen.
Violet represents love. Sort of unique, as they don't create Violet Lanterns, but Star Sapphires (Star Sapphire is a long-standing GL villain).
And, of course, green represents willpower, bravery and the ability to overcome great fear.