Undercoat with Skull White or any other suitable white paint.
Wash with Agrax Earthshade .
Wash with Lamenters Yellow or Iyanden Yellow or any suitable yellow wash. If using contrast paints make sure to dilute to a wash consistency.
Wash with Biel-Tan Green or any other green wash. For bigger more experienced Orks maybe Waaagh! Flesh or smaller weedy grotz maybe Warp Lightning If using contrast paints make sure to dilute to a wash consistency.
Dark Metal
Basecoat with Revell Aqua Colour Tar Black
Wash with Orange
Drybrush with Necron Compound
Wash rivets and recesses with watered down Skrag Brown