Green forest camouflaged armour with blue overalls - kinda like in Avatar. I loved this colourscheme when it first came up in the random selection on Dawn of War. You can also see my progress on a devilfish with this paintscheme.
Another option is urban camouflage I'm not sure how this will look but it might be something like the following picture. This should definitely be considered as I play a lot of cityfighting.