In MODERN terminology "Red Brass" means something with a nominal 85% copper, 15% zinc. It does have a reddish cast, as opposed to the cartridge brass we all use. Red brass is good in plumbing fixtures, with more than 15% zinc the zinc tends to leach out after some years in tap water.
The "brass" used for US Military gun hardware, both horse pistols and Colt revolvers, was somewhere around 78% copper 18%zinc 3% tin, with just under 1% lead for castability. It looked about like modern brass.
Eventually 19th Century Guys learned that the maximum strength, and minimum cost, brass was something using 70% copper 30% zinc. Practically speaking that is about as much zinc as one can add to copper without making a brittle alloy (e.g. Muntz metal, 60%copper 40% zinc) So today when you buy brass, also called C260 (cartridge brass) or C360 (leaded, free-machining brass) you (usually) get something with about 30% zinc.
When it is new. Ah, but some corrosive environments can leach out some of the zinc, leaving your brass with a reddish cast. My old cat with an upset stomach taught me that, leaving reddish pitted areas on the lid of an antique brass charcoal warmer. In general, when brass corrodes it looses zinc from the surface, leaving a reddish color.
I suppose if you want your brass hardware to look really old or Southern mountain style, you should search out some red brass, the (seldom used) specification being UNS C23030. I've bought free-machining brass bar, round and flat, from metalsonline. Think they have red brass pipe, but I personally do not know where to buy Red Brass sheet.
