Continentals generally followed British practice in this regard during the first half of the war, although as Cornet says, some units went for alternatives and many had more important issues to address. Sometimes musicians would just have lace on their uniform; occasionally, they were given captured British infantry coats (especially from regiments with blue facings, as these "reversed" one of the most common coat/facing combos).
The "official" regulations in 1779 provided for all units to have reversed colours for musicians.