Sheets of colored plastic (for darkroom safelamps?) (Seaside BN23)

New as in, these pieces haven't been used. Two rolls. Red is 24x14 inches. Yellow is 20x15 inches. The yellow one has been folded at one end and has two pieces of Sellotape. I'm assuming that these are for darkroom safelamps as I used to do darkroom work about forty years ago. But I may be wrong. They could be useful for arts and crafts, window decorating, other stuff.