Between Pink and Blue, I believe it's just the color. Both are what's called Extruded Polystyrene as opposed to the white dots that's called Expanded Polystyrene. Same material for the most part in all just different processes and colorings. Pink for Pink Panther - Owen's Corning verses Blue for Blue Dow Board. A look at the R-Value and any
MSDS data for the board should be able to confirm blue and pink are the same.
By the way, it's not flame resistant and it's poisoness if it burns so there are certain
safety precautions for use with it such as flame treating all sides and only a certain percentage of the
stage area that is allowed to have it given a
smoke trap door or other fire
safety features which will let the
smoke and poision out. That is I believe such regulations are about standard. Don't think foam is flame retardant but again that should be clearly posted on the board if it is - they would want to brag about it. Look into that. Gesso/Scenic Dope/primer especially if Phlex Glue or Sobo making up the scenic dope (as opposed to white glue that does not stick as well) will coat it and provide some flame resistance to the front
face but the rear and other sides will need other protection.
It's also damaged by UV and heat such as a light focused upon it. Plus it does not like to be carried on the roof of your car.
As for attachment, 3M orange "Foam Fast" works really well, otherwise there is some contact cement specifically designed for foam on the market. Liquid Nails works sometimes depending upon the lot number. Some lots of it will burn
thru, others will work fine. There is panel adhesive sold in gallons also that's made for attachment but it will not bond as well as the above three. All the above is also flammable.