I considered a blue lantern before I went wiki diving. Their rings are totally and completely useless without a GL around. All it does is let them fly and survive in space.

A Red Lantern would have to act a bit too much like Sentinel, and I don't feel like playing the same character.

Larafleeze is the only orange lantern.

Indigo would be very unique, and could have been interesting. But I like to characterize, and Indigo's are allowed to be (ironically) unique.

Star Sapphire...I only really play male characters since I'm a guy. I don't wan to fall into stereotypes and cliches, and I'm afraid that would happen if I tried to play a female. The only male SS has been Jon Stewart, so I don't see that as an option either.

Black and White are both off limits for obvious reasons.

I could see a yellow lantern being a possibility. However, he wouldn't fit well with the team dynamic we're going for and the rest of his Corps is kind of super evil so that would be an issue too.

Overall, green is just easier.

Speaking of lanterns: Could we pretend the last major GL event was Brightest Day? War of the Green lanterns and Third Army both heavily tie into the New 52; which we're ignoring, so that would turn out messy real quick. This would mean that, in a nutshell:

Hal Jordan is a Guardian of the Universe.

The Guardians aren't totally off their rocker crazy pants

Guy and Kyle are both GLs and members of the Honor Guard

Simon Baz never happened.

This would also mean that the assigning of another Lantern to sector 2814 would make sense. After all, Jon Stewart is technically the only lantern for this sector and each sector is required to have two lanterns. Hal Jordan could still operate from Earth, but he'd have responsibilities across the universe. The same can be said for Guy and Kyle, but they would probably be more earth based than Hal.