here's the scheme that ive been using on my own Iron Snakes:
The way i did this was to spray a black primer coat then basecoat in Boltgun Metal. for the gold parts, i painted light coats of shining gold over the boltgun. The red knee was done in Scab Red over the boltgun as well.
The shoulders: the white part, i went with a basecoat of Astronomicon Grey, then thin layers of Skull white, with the edge being done in scab red.
over all the metal colored bits, i used Asurmen Blue wash, followed by washing the entire mini in Badab Black. To finish up, i did a couple streaks of boltgun metal over "highlighted" areas. The eyes were done with Enchanted Blue, with a bit of Ice blue over that.