The liquid air article on wikipedia doesn't have any photos.

https://en.wikipedia.org/wiki/Liquid_oxygen

Air is blue. The reason air is blue is blah blah blah physics, see the article we're all commenting on, but at the end of the day air is blue. We don't demand the same elaborate physics questions for why a ripe banana peel is yellow.

So was blue intrinsically pretty and thus made into the sky, or considered pretty and thus imprinted in the minds of humans that way?