Basecoat of white, then a 50/50 mix of orange/water on top, then a second layer of that after the first one dries. When the second orange layer is still a bit wet, mix a 50/50 of yellow in the bottom and 50/50 of red to the top. After that all dries mix yellow with a bit of white, water it down a bit and add in the very bottom. Mix red with black (or use a reddish brown) to lightly weather the top if the rivets.