I believe both the pink and blue versions of this rigid foam have a thin plastic film covering the actual foam. You'll find that things like plaster and adhesives will bond a lot better if you first peel that film off.
Be advised, though, that once that film has been removed, the exposed foam will create dust if anything abrades it....like clothing! And, worst yet, that dust will be looking for anything amicable to a static charge! Pink or blue versions...it's the same for both in my experience.
The suggestion to experiment with small pieces of foam, plaster, rock moldings, adhesives, etc., is a good one. It's kind of hard, for instance, to describe the best plaster consistency for vertical sticking of molded rocks. You'd do well to evaluate that for yourself.