I found a box of discarded keyrings with transparent fobs at our Habitat Restore a few years ago. The local Ford dealership had changed ownership and the name on the fobs was wrong. I got a good price for the whole box of keyrings.
The fobs are linked to themselves with their split rings; the top of each chain is hung on a curtain rod. Most people just see a pretty turquoise curtain; only people who take a second look notice the printing on the fobs. The blue circle in the middle is two cracked plastic dinner plates, hung from wire. The decorations on the back of the plates create a moire pattern in some lights.
I dunk the entire assembly in the bathtub once a year and let it drain over a clothes rack until dry.
Addition: The other day I noticed a play of colors on the fridge.
I can’t think that I had seen the keychain curtain casting colored light into the kitchen before. It caught the exact angle of sunset at a time I was there to see it.