Thaks Mike, that's a simple drybrush of silver on a black undercoat.
As usual my picture isn't that good... I'll hire a professional photograph for the next LPL
Look into setting the white balance on your camera. There's probably a colour mode better suited for whatever lighting you're using, and a lot of even quite basic cameras can do custom white balance these day, even my current Android phone can.
Basically you set up your scene and lighting, then hold a white object in it (a piece of card or paper), focus on that white thing, and take a photo; the camera is then able to use that as a reference point for colour balance.
The robots look good, I'd kind of like to put together a group of clanky old-school 'bots for a pulp team at some point, either independent or lead by a proper Mad Scientist Type!