http://roosterteeth.com/episode/rwby-season-3-chapter-1
Emerald (green hair) and Mercury (silver hair and costume) are actually villains, but the other characters don't know this yet. They've infiltrated Beacon Academy posing as students in order to suss out the fighting style and weaknesses of Ruby and her team.
Nora reminds me of Overly Attached Girlfriend.
Lie Ren - Nora's laconic partner in green - was originally voiced by Monty Oum himself; he's now voiced by Monty's brother Neath.