It has to do with what frequencies of light the object reflects well, which has to do with the atomic structure of the object at it's surface.
It's really quite a complicated question as to why this surface reflects red well while this one reflects green well and to really get an answer
you're going to have to delve into quantum electrodynamics which is not a topic for the faint hearted.
what gives light-reflecting objects various colors?
You might think of it as which colors (which electromagnetic frequencies) the object absorbs. Then, it reflects the rest.
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If it has VARIOUS colors, it is due to diffraction of light from the surface .... kinda like a prism splits white light in to its component colors.
In one of the Feynmann lectures he goes deeply into why a drop of oil on a water surface has all the colors it does.
It's one of the best explanations of the quantum nature of electromagnetic radiation there is.
I don't know if that link will cause this to go into moderation limbo or not... we'll see
It does. Just youtube Feynmann lectures, and look for Part 1 - Photons Corpuscles of Light
It just sometimes (maybe always) needs a moderator to ok them. I even have to ok my own ones.
Usually there is a moderator comes by fairly quickly.
Yah....I was thinking more like a fresnal lens...or one of those bits of plastic with a bunch of very fine concentric grooves engraved on the surface ( kind of like an old vinyl LP).... I understand what you are posting too....... ~ EP