How many eps are there for S2?

13  episodes.

In a January interview with Collider.com,
showrunner Ryan Condal was quoted saying:

"... The benefit is that this kind of storytelling is so much better suited to 13 episodes because it lets you go down those little avenues.  When you have 10, you’re like, 'Okay, this is the one large arc that we’re telling this year.'  This" [13-episode season] "allows us to have three chunked out arcs, and then the one big arc that goes over the whole thing. Those little avenues that you’re able to go down make one-hour drama great and different from a mini-series or a feature film. ..."
   http://collider.com/colony-season-2-josh-holloway-sarah-wayne-callies-ryan-condal-interview/