What color is solid methane?
Your question is not very specific. So the answer is it depends. Think of water as an analog. 


Methane "snow" would be white. (Due to scattering of light). 
Solid methane under sufficient pressure would form a clear colorless solid. 
Methane "snow" (which would be on surface" of some celestial body) could be any color if contaminated by even small amounts of other hydrocarbons. A reddish color seems to be typical. See ref: http://www.caltech.edu/news/astronomers-find-ice-and-possibly-methane-snow-white-distant-dwarf-planet-1714