Source of the post
Gasses usually reflect different wavelengths of light, so it'd make sense to code the atmospheres with their constituent gasses.
This is a common misconception, but a misconception it is (and Space Engine is kinda contributing to it). The color of an atmosphere has very little to do with what gases it's made of. It depends on something else altogether: what kinds of suspended particles and droplets there are in the atmosphere. Clean(ish) atmospheres tend to be blue due to a phenomenon called Rayleigh scattering, which is very little impacted by what molecules the atmosphere is made of. The Earth (N2
), Uranus and Neptune (both H2
, He, CH4
) and Pluto (N2
and CO) all have blue skies, despite showing totally different compositions. The same goes for the upper layers of Jupiter's, Saturn's (both H2
, He) and Venus' (CO2
). "Dirty" atmospheres show other colors, and the kind of "dirt" will determine the color. In the case of Mars it's its rusty dust making it pinkish; in the case of TItan it's several layers of hidrocarbon hazes (small droplets) that turn it orange.
SE now shows a number of different atmosphere colors that may make for pretty pictures (they do) but are largely unrealistic. I don't know what kind of particles (short of aereal phytopolankton, I guess) could turn an atmosphere green, for instance.