You will need snowpants. You will die if you want to just wear leggings or yoga pants. Luckily there are slim fit pants. For pants I'd recommend black/tan/khaki. White gets dirty and I am not a fan of bright colors for pants. I like plain pants and then you can get any kind of jacket.
These in black would be dope:
http://armadaskis.com/products/outerwear/womens/whit-pant/
If you can spend a bit more I'll suggest orage:
http://www.orage.com/us/clara-pant (I like the black)
http://www.orage.com/us/chica-pant (I like the black or either shade of tan)