I'm planning to paint these orks as Death Skulls with their signature blue warpaint and lots of looted bitz. For colours I'm thinking of a basecoat of Knarloc Green, shaded with a Dark Angels Green wash and highlighted with Goblin Green and Scorpion Green. Blue will be used as a spot colour on the face and weapons. Basecoat will be Mordian Blue. I'll higlight this with Enchanted Blue and Ice Blue with a little Bleached Bone mixed in.
I don't have a codex so any suggestions for an army list are welcome.