The color of the Earth's atmosphere is pretty well determined by the size of dust particles and aerosols in the atmosphere which have sizes close to the wavelength of optical light. It also depends on the spectrum of the Sun. We could also change the color of the atmosphere by loading it with the right gases and dust grains which would absorb all of the light except those wavelengths at which the desired color would occur. As I recall from chemistry, chlorine gas is greenish, so an atmosphere of chlorine would have a greenish tint.
As for the color of stars, their color would be affected by the constituents of the Earth's atmosphere such that for the present atmosphere, their light gets slightly reddened as its blue component is scattered out of the beam by the same particles that give our sky its blue color. Atmospheric reddening is strongest towards the horizon where the path length is greatest, and this effect is easily measured by careful observations of stars through a set of specially-made filters.
Yes, I suppose that with the right atmosphere, a star's color could be made to be anything you want by a suitable combination of dust sizes and gases. Our atmosphere is dominated by nitrogen and oxygen which are colorless, so if we removed the dust, there would be no spectacular sunsets. Adding chlorine in large quantities would give the atmosphere a greenish hue but such questions are pretty hypothetical to organisms like us!
Copyright 1997 Dr. Sten Odenwald
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