If you're using an Ecaller and placing it several yards away from your location, than I wouldn't worry too much about camo, since the coyotes would be looking to the sound. If you're using hand calls, simply find some vegitation that is not totally covered in snow and is as tall as your are in the sitting position, and sit in front of it. Don't move too much at the wrong time, and you'll do fine.
I sometimes hunt with a rancher friend of mine that seldom wears any camo., BUT he doesn't do the calling so the coyotes don't pick him out because they tend to concentrate on the source of the sound.