Styrofoam pieces as plant medium use

[ladyslipper]

Hi guys, quick question (almost embarrassed to ask). I took delivery of a package today that had styrofoam pieces to protect the contents. There were quite a few pieces that were blue or yellow. Are these safe to add to a medium or should we stick to the white pieces.

Just had to ask in case having the coloured pieces so close to the plant would be toxic over time if in contact with water frequently.

m