As long as the poster knows Blue Styrofoam (EXPS) by Dow Chemical from bead board (EPS) The White Cheap Stuff.
Styrofoam is Blue, and is a Registered Trademark of Dow Chemical Co. It is a closed cell extruded polystyrene insulation. It is so resistant to water that it is used in inverted configuration in low slope roof systems where it is placed on top of the roof membrane. (Protected Membrane Roof System).
And Yes, we need to know where you are to know where the Vapor Barrier/ Retarder should go, but Generally Speaking you want the dew point to fall in about the middle of the insulation package.