Question

What will be the colour of the sky on a planet that does not have atmosphere? Why?

Answer 1

The sky on a planet without an atmosphere will appear completely black.

This happens because the sensation of color in the sky is entirely created by the scattering of sunlight by gas molecules, dust, and water droplets. When a planet has no atmosphere, there are absolutely no air molecules or particles present to intercept and scatter the incoming sunlight in different directions. Since the light waves pass straight through the vacuum without any deflection, no scattered light enters our eyes, making the sky look pitch black even during the daytime.