I just started painting the robots. Using the hairspray weathering technique, I chipped away the black paint, showing the red underneath. The thought was to have the robots black, but really weathered. So I went with a strong contrast on the weathering, that also made them fit better into the rest of the army. Therefore I chose red, which is the main colour of the army. The red underneath can be the colour of the robots previous allegiance, or some weird form of rust or corrosion. I'm not yet sure what the red is supposed to be, but I like it so far!