I also don't see how only Red and Yellow are shown as "evil"
Oh, certainly they aren't. They're just the most obvious. The Greens are clearly the only good guys, and even then it's not actually the whole Corps, it's just those plain ordinary folks on the line like Just Plain Good Guy Hal and not the guardians or their reprogrammed Alpha Lanterns. The Blues are a bit nebulous at the moment, Walker and Ganthet being obvious white hats, but then, they're led by Ganthet and sucking Hal's Super Special Savior cock and their rings don't function properly without green energy, plus there's that ominous "cost" business, so I'm not sure they actually qualify as a separate faction. Certainly they're not an organization with their own goals, interests, and powers in their own right who stand as equals to the Green Lantern Corps.
Which, again, I find utterly uninspired. Lazy, even. Look, everyone who's not Our Heroes is a bad guy with a net negative influence on the galaxy. This total uniformity from a concept that should have provided such an awesome diversity of motives and behaviors and activities is just such a dull waste.