Both, plus some really odd ones. People left guns in North America when the SYW/FIW ended, and they got taken up again in 1775. See Fort Ticonderoga for the most spectacular example. The Americans cast very few, and to British patterns. Guns get captured back and forth over the whole war. The British ship over new artillery units, but they haven't redone their artillery since the last war. This is also true of the small number of guns associated with German units. The French ARE in the middle of changing from La Vallerie to Gribeauval. The smart money seems to be that their "foreign aid" to the Americans was La Vallerie, and any guns actually manned by French gunners would have been Gribeauval. Siege guns are often a little out of date anyway.
But these are all--except for ship's cannon and fortress artillery--double-trail guns. What scale are you building in that you could tell them apart?
Oddities. You find a few "grasshopper" and possibly a "galloper" gun or so--very small caliber, never more than two at a time, and associated with light units.
Colors. Lots of argument. MAYBE British in gray or dull red, Americans in dull red or possibly light/medium blue, French possibly in a darker blue and the small German states imitating Prussia. Not by any means certain that captured guns were immediately repainted, that anyone was enforcing a paint color, or that colors were consistent over space and time. If we were sure what color Burgoyne's guns were at Saratoga, we still couldn't be certain Cornwallis' were the same color at Guilford.
A couple of suggestions. Anything CAST in North America would be iron, and so the barrel probably painted black as a rust preventative. As for painted woodwork, I suspect there was a lot of "barn red." You can make it on the spot with surplus milk and rusty iron, and everyone was at the end of long and uncertain supply lines.
I would, purely for wargaming purposes, pick a gun color for the Americans and one for the British and stick with it. (You have to look for German guns, and the French only do sieges, which I find deadly dull.) But within those broad limits, people will be hard-pressed to prove you wrong.
And if anyone has something definitive, please say so. I'd probably repaint some guns to match.
paints brigs for the British fleet.
