Question

What happens to the colour of sky if therewould be no atmosphere

Answer 1

In absence of atmosphere and molecules of air would lead to no scattering of sunlight. Sky would look pitch dark with bright stars and sun. Sun would appear white and brighter in the dark back ground.

Answer 2

If there's no atmosphere then the colour of sky should be black.

As there's no atmosphere to scatter the light.

Hope it helps.