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

The sky is blue because of Rayleigh scattering, not refraction.
Briefly, it is dependent on the wavelength of light( blue shorter than
red and yellow) and the dimensions of oxygen and nitrogen . 
But for or a good easy-to-read discussion, see Trefil's 'The Unexpected
Vista.", Ch 11 : Why the Sky is Blue?" 
You'll see how there's also a connection between why the 
sky is blue and why the sun seems yellow when it's up in the sky.

When radiation passes through a layer of solid,liquid or gas,
cetain frequencies may be selectively removed by absorption, a
process in which electromagnetic energy is transfered to
the atoms,ions or molecules in the sample. Chlorine is green
because it absorbs reddish frequencies and reflects "unused"
green.

The colour of a substance often changes with a change of state.
New intermolecular bonds are either formed or broken, and this
changes the way matter interacts with light. Ice, for instance,
is slightly bluish because it absorbs red as well as infrared.
Infrared causes molecules to either bend or stretch.The vibrating
bonds will absorb energy from the radiation
if the frequencies of the light and the vibration are the same.
In a liquid state water's molecules will spring back in forth
when absorbing infrared, but when they're tightly bound in the nice,
hexagonal structure that is ice, H2O molecules will behave differrently.