Explain by giving

Sky appears blue due to the phenomenon of scattering of light by the molecules of air and other particles in the atmosphere and since they have a size smaller than the wavelength of the visible light, so the particles scatters blue color light rays effectively than that of longer wavelength color.

The color of the sky is dark instead of blue to an astronaut because there is no presence of atmosphere in the sky due to which the scattering of light doesn’t occur and the sky appears dark.