Future War Cult (FWC)
If I had to pick a faction based off of names, well... Osiris and Dead Orbit seem too depressing (let's base our name off of dead stuff!) and New Monarchy seems too hoity-toity for my taste. Future War Cult seems pretty aggressive. Seven Seraphs, though? That's something I could give my vote to.
If it was based purely off color scheme, Dead Orbit. However, I have a feeling they're going to be a little too religious for me tastes. Just based off their name, they seem to have a worship of the Traveller. Don't know if I'm down for that.
i personally think we don't know enough about them yet to make our final decision