A few years ago, Jeff McWhinney, working for 3M at the time, gave me a sheet of diffraction grating film, which breaks up light into all the colors of the spectrum. I put it up, covering the south-facing window high in our office and in the afternoons, we have rainbows moving through the office, changing as the sun moves inits pattern through the sky. I walked into the office just now and wow, check out my computer.
In the ’60s we used to get this stuff (along with prisms) from Edmund Optics (which we learned about through the Whole Earth Catalog). Fahr out man! And still is.