Yeah, Shas'o Fal'shia Kais Or'es (that's a mouthful) hit it right on the nose. The blue they use in the 'eavy Metal stuff is Ultramarines Blue (perhaps a little darkened though).
I've seen Regal Blue used to good effect to make them a little bit darker. Another good trick for a darker, grittier look (Who cleans the armor if the men are no longer inside...?) is to apply an ink (black, chestnut, maybe even a dark blue ink) over the gold and yellow areas.