Bondo will dissolve any kind of polystyrene foam---white expanded bead foam, blue or pink insulation foam, etc.
The solvent in Bondo is styrene monomer. That's a liquid made of single-unit styrene molecules or "monomers." That liquid will dissolve polystyrene molecules, which are "polymer" molecules made of chained-together styrene units.
You can seal polystyrene foam with epoxy so that you can put Bondo over it without dissolving the foam.