Very cool this head. Could make it lighter (in the middle), a metallic bleaching (a gloss, or the area to be unpainted, representing the area of greatest concentration of light.). The eyes are really cool, you can place a poco de neon (Slightly on the shaded) think it would be cool.
Since this is a robotic head, could leave more aged it (an already worn metal)
Which program you are using to make the head?