Subject: Is the color of gases due to reflected or refracted light?

The sky is blue I think (correctly?) because of refracted light.
Oxygen and nitrogen gases in a bottle on earth have no "color".
What color do they have when they are liquids or solids?
Is chlorine gas green because it relects green?
How do the different states (solid, liquid, gas) affect the color
of a substance?
If the color does change with a change in state, why does it change?
Perhaps crystal formation plays a crucial role,
What if no crystals are formed? (Etc.)       Thank you

Re: Is the color of gases due to reflected or refracted light?