Question

What would have been the colour of the sky if there had not been any atmosphere around the earth?

Answer 1

Since the scattering of light is due to the fact that the smaller wavelengths of the visible spectrum are small enough to be obstructed by the particles in the atmosphere, whereas longer wavelengths would be obstructed less. If there is no atmosphere on the earth then the light will not get scattered and the color of the sky will be entirely black with a bright white spot which is the sun.