One of the best combos you can run is white pants and a dark top. That matches well with most cover since the white matches the snow on the ground and the dark top matches trees etc.
You can find cheap winter whites at Canadian Tire in the hunting section, and even at hardware stores if you get the light painter overall. What will work best of course depends on your local conditions and temperature. Some of the cheap ones are cotton and pretty easy to get soaking wet in the around zero zone.
Airsoft, where nothing is hurt but feelings.