I kept it mostly monochromatic with the only deviating color of green on the sword and eyes. The armor on the arms, legs and hands were all a mix of Vallejo dark and light grays airbrushed on, then lined with black ink and edged with light grey and mixed in white gradually. I'm not too fond of how the pants turned out, black cloth has always been my bane. When I try to airbrush the color on it always turns out too gray. When I try to brush it on it doesn't look right. I ended up brushing it on, then the mix seemed way out of whack, so I knocked it back with a heavy black wash and said screw the rest, it's passable.
The green is an interesting story. Since I don't have many primary colors for airbrush and didn't feel like trying to thin out my GW for airbrush I just found my blue and yellow VMA paints. Yellow mixed with blue is green, right? Well, it is an extremely dark green, even with a bright yellow. I ended up wasting a lot of paint trying to get the mix right. It took a hell of a lot of yellow to make a regular green like snot green, then I lightened it for the highlights by adding white. The last highlight was almost all white with a small bit of the original mix.
I've still got the base to paint, along with his accessories like the grenades and pistol/case and glowing forearm thingy. But I've liked the results so far so much I wanted to post my progress.
I'll keep you posted on further painting updates!