There are some very interesting alternatives, depending on what else you're fielding. Early war there were a lot of Americans wearing brown coats, faced in red, blue, or yellow, depending on which regiment.

You could also potentially do them in captured red coats with yellow facings, as Webb's men famously wore. It would be a bit confusing on the tabletop, but then it was confusing in real life, too.
I'd go with brown.