It's not bad. It looks a little simple, but not badly put together. I would recommend different joint colors, though; maybe Juryo and something; demon/void would look best, but they're expensive :x
If you want to keep the green, I'd recommend putting some green accents on the body textures and perhaps on the head as well (kind of like what's happening with the triceps).
^
i agree with the saru
and maybe put some green on the hands and feet