[jxdxbx]

Yes, I came here to say this. The whole topic drives me crazy. Air is just blue. Everything is a color because of some physics reason. Some birds have blue wings due to microscopic structures and how light interacts with them, rather than pigment.

If you took a large column of air into space and shined white light through it, it would be blue.

[rcxdude]

No, it would look red. The weird thing about air is that it's not reflection or absorption that gives the color, but scattering, and that means the color is strongly dependent on what direction you are looking at it from in a way that most transparent mediums aren't.

[jxdxbx]

Ok, so the air would be red from one angle, blue from another. In each case, that is what color the air “really” is, in the same sense that a butterfly’s wings are blue (but not from every angle)

[rcxdude]

Except that one is transmissive and the other reflective. They're not the same kind of thing. TBH I feel like a demo like this is the only way to get an intuitive feel for it: https://www.youtube.com/watch?v=-Xx7sPPTu3Y .

(I agree that just going on about Rayleigh scattering is probably overly obtuse: at least not without explaining that scattering is part of how color is formed in the first place. But it's also not just a case of 'well air is blue like apple juice is orange')