Why is it when you look at some things really close up, you can see rainbows colors?
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It’s because natural light is not a single color, it’s a bunch of different colors (lightwaves) mixed together.
When we observe color, we don’t see the surface of the object, we only see the light that is reflected back at us.
If light is like a group of people queued up to enter the club,
then each different surface is like a bouncer denying entrance of people who wear shirts of color he doesn’t like. When Alice who’s wearing Red shirt, Bob who’s wearing Blue shirt and Charlie who’s wearing Green shirt want to enter the club, the bouncer will tell to Charlie “go away”, because he doesn’t like green color. Bob and Alice will “be absorbed” into the surface, but Charlie will “bounce” back to our eyes, so we will think that the bouncer of that club doesn’t like Green.
There is also a natural phenomenon [[Thin-film interference ]](https://en.wikipedia.org/wiki/Thin-film_interference), where minuscule differences in thickness of the layers will bounce light differently.
I think the particular thing you’re talking about is [diffraction](https://www.exploratorium.edu/snacks/diffraction), which is due to the wave-like nature of light.
Basically if you look really closely at the edge of an object, or a very thin object, light actually bends around it a bit. But the amount of bending is dependent on the wavelength of the light. And what we perceive as *color* depends on the wavelengths of light. So, red will bend a lot and green less and blue less than that. As a result, we see a spectral distribution of these wavelengths, that rainbow-like effect. (Rainbows, by the way, are the result of reflection and refraction, not diffraction. Refraction involves light bending not around edges, but because of encountering different materials. But all of those processes involve the wave-like nature of light, so they are all related.)
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