Steve,
Porter early on was using very standard paint on locomotives. Primarily the entire locomotive would have been black with Gilt (gold leaf) or Imitation (yellow) lettering. Based on the typical appearance the boiler all the way to the backhead would have been wrapped in planished iron, as would have been the cylinders. The cabs on porters unless specifically requested would have been painted the same overall color (black) with a natural wood interior, cab window sashes would have been varnished wood as well, also of note the bell would have been painted the same body color (black again).
-=Andrew=-