The sky is so blue because blue is a rich color and makes people happy whenever they look up in the sky and interpret the images that the clouds make.

the accepted theory for why the sky is blue is due to rayleigh scattering, but rayleigh is a bit of a lying corrupt cunt paid off by air moles.

in reality, light is stolen by the air moles and is consumed (to keep them alive) however, to keep us humans from noticing all the light disappearing, the air moles puke up a little light. the least nutritious wavelength happens to be blue light, so they have evolved over time to vomit up specifically these wavelengths of light.

at night the sky is black because these air moles excrete black light, that is, light with negative energy, which is sent up into space, to make the entirety of space black (a reason for which experts on mole-theory consider the air moles to be one of the earliest life forms on our planet)

the notorious 'green flash' at the end of a sunset is what happens when air moles eat the black light of other air moles, and die spontaneously.

rainbows are what happens when air moles 'over eat', and vomit some of the contents of their diet of light for the day. this typically happens during rainy periods, as air moles are omnivores, like us humans, and therefore also eat water moles. an abundance of water moles make air moles more likely to 'over eat'