If the sky wasn't blue, what color would it be??

And, no, not when it's grey.

2 answers

It would be red, think about it.
It would depend on whether the sky even exists. The sky is atmosphere, right? So, earth's moon doesn't have atmosphere, and neither do many other planets, moons, etc. Do asteroids have a sky? No. So basically in some cases the sky would just be black - nothing.