I'm working on slowly but surely painting my Betrayal at Calth box. Next up on the "finished projects" table is the Contemptor. I did magnetize the arms at the "elbows", so I can swap out the fist for the multi-melta and so forth.
Painting recipe for this is: prime black, base
GW Air Leadbelcher, Minitaire Ghost Tint Blue from the bottom upwards, then Ghost Tint Plasma Fluid from the top down. Note that the more coats of Ghost Tint you do, the deeper/darker the color gets. The weathering/base colors are a mix of various browns, including Skrag Brown, and Secret Weapon weathering pigments.