White or Pink Foam?

[GreenDiesel]

My son & I are planning to rebuild our 28.5" x 68" layout. We have a sheet of white styrofoam that I bought from Home Depot. It seems strong and sturdy. But we want to do things right this time. We don't plan to dig down into the foam but do plan to build & add scenery on top of it.

Is it OK to use this white sheet of foam or should we purchase some of the pink or blue foam?

TIA.

Rob