Let's be real. The sky is blue because God thought it was a pretty color, simple as. All this stuff about wavelengths and resonant frequencies and human color perception got retconned into the physics engine at some point in the past millennium, that's why all these epicycles are needed.
Our lord Zeus always thinks of everything
His noodly appendage touches all.
> thought it was a pretty color
So was blue intrinsically pretty and thus made into the sky, or considered pretty and thus imprinted in the minds of humans that way?