# What would a planet's sky look like with different chemical compositions, such as low nitrogen, high methane etc?

What are the processes, chemicals and particles involved in creating colour in a planet's sky? Could you give some examples of sky colour processes different from what happens on Earth?

Except for Rayleigh scattering (Is the color of the sky the same everywhere on earth?) gases typically do not add any color to atmospheres, they are usually transparent in visible light. The Halogen gases (F$$_2$$, Cl$$_2$$,Br$$_2$$, I$$_2$$) have color though, and there are a few other colored molecular gases, but you would not expect them in planetary atmospheres.