I have seen some very good winter camouflage done using a thinned down white airbrushed over a green undercoat, then weathered with paint chips and mud and rust streaks. The best example is on IPMS, showing the technique on a US Sherman.
So this tank started out base coated with a Krylon camouflage green spray paint i picked up at a local hardware store, serving as both base coat and primer. I then gave it a patchy whitewash using thinned Tamiya paint applied via airbrush. On top of this i tried out a technique I saw on battlefront, using a bit of sponge foam to apply paint chips in green to the edges of the tank.
Improving on my last build, the tracks were coated in a glue/sand mixture and painted to resemble a mixture of mud, filth, and road grime. In addition to the green paint chips, some areas were further weathered with chips down to the bare metal itself, which would have rusted in a prolonged winter campaign.
Overall, I am really most pleased with the tracks, but somewhat disappointed with the rest of the tank. I may remove the tracks, strip and repaint the rest of the vehicle.