Right now, the sky is blue, but it's freezing :/ It's not a clear blue, it's dingy because the weather is weird in Ohio.
It is gray here today.
My dad, had my cousin convinced that the sky was green and grass was blue. So I'd say green.
The sky does not actually have a true color but is merely translucent. It is the refraction of the blue wave length of light, mainly, from the sun that reaches our eyes that gives the sky a blue appearance to humans. Different animals do not see the sky as blue.
Forget all the twaddle. It's blue. There would be no colour at all except for Rayleigh Scattering that makes the stuff you can look at rather blue.
It's late, and I can't be bothered to explain more than that.