I second (or third) the motion to do what pleases you.
As demonstrated in earlier posts, bluing, browning, and in the white were all options in the late 18th century. Since no one in the c. 1780 ads describes browning as the newest and latest revolution in metal finishing, it's safe to assume that, while it may not have been the most common, it was an established technique at the time.
The tone of some of the other posts above once more reminds me of the gun store owner and collector who, after being shown photographs and written descriptions of 18th century rifles that didn't conform to his view of what such guns should be, told me that, "Those guns may be original, but they aren't correct." The arrogance of such a statement almost takes the breath away.