The M-1919 was issues with a bakelite and a rubber grip, but the collectors tell me those are very rare for not lasting long.
Both walnut and birch were used for the grip. The latter were stained dark before having boiled linseed oil rubbed in. One thing about BLO is, that when left in the sun, it can 'cook' to a rather dark color.
WWII Parkerization had a distinct green cast--drop of green zinc chromate, drop of black green added to Steel will get close. After the war and through KW, the parkerization spec changes to a charcoal grey--about equal parts Steel and Sooty Black (or use Burnt iron with a couple drops of Aluminum--I've not tried that mix).
For 1919 barrels, my method is to paint barrel & shroud in NATO Black. Let that dry, then 'wet' drybrush the shroud in a mix of Steel and Oily Black. if you are really tough, a 2H pencil will give a nice highlight to the barrel--but you need a ruler, a magnifier and a base course that keeps the ship's roll to a minimum.
Now, for colorful, nothing but nothing beats the Browning 1917. Receivers are often Colt's Imperial Blue. The cradles have bronze and brass and plued as a well as phosphated parts. The end caps on the water jacket are a brass color, ranging from pale bronze to brass to gold. The tripods are usually a Medium Green (the 4-clor NATO, not the SEA air force). Although a replacement leg in OD is often seen.
Ok, so the Brit Vickers has even more color combos--but, I stick to US subjects.