The basic concept of the Silver Age Green Lantern was that the Guardians of the Universe created an intergalactic police force that would patrol various sectors of space, armed with a ring that could do more or less anything the wearer wanted it to with sufficient willpower. All the energy in the ring came out looking green, and that was that. Originally, a single yellow ring was worn by former Green Lantern turned bad guy Sinestro. Writer Geoff Johns explored that concept, and came up first with the idea of another Lantern Corps armed with yellow rings like Sinestro’s. And hey, if you’re going to have rings that work off green (willpower) or yellow (fear), why not try some other colors?
That’s where Dex-Starr comes in, one of the most tragic anti-heroes in recent comics. Yes, it is tragic.