Hmmm, difficult one.
I think white is the only color to use when reflecting snow, but I would blend it with grey towards the horizon. For the sky, use a darker colour than normal. I\'ve seen models that started with light blue and blended into almost pure white. I think when you do this, the metal will look too white. So my suggestion is to create a darker sky (blue, or something like dark clouds).
These are only suggestions, I have never tried this!!