HG Wells has the Martian craft as metallic. Problem there is that could be a bit dull, especially as the bridge girder work will be the same. So how to jazz it up? Well, I've got a pot of Citadel Metallic Green that I've had for a good 30 years and is still viable. So, after basing in gun metal, I've dappled on another coat with some of the green mixed in. A bit bright, but the next stage will take care of that.