I have seen a couple Vincents over the years. I am not sure how they left the shop but they had a "dull grey" metal look 125 years later. Almost like they were left in the white and allowed to slowly turn brown over the years.
Some builders here have achieved that look. I think they use a cold blue solution and allow it to form a little surface rust, then card it off and either repeat for a darker color or follow application directions to stop reaction.
I have left a couple in the while and if properly cared for, gives a real nice looks over a few years. I would try leaving it in the while. You can always changed it down the road.
Brian