Answer: (2) Black
The atmosphere gets thinner and thinner as the astronaut travels farther far beyond the earth atmosphere. Space does not include any particles that can allow the scattering of light. It is therefore empty, that is why, in the end, the moving light disappears in the distance. This is the explanation why the colour of outer space is absolutely black.
The sky that a normal human being sees in the daylight is blue. It is due to fact that many particles in the environment are hit by light produced by the sun. It allows it to scatter, resulting in a blue colour. But it not the case in outer space.