It may have been for a very specific use. Wash the truck down with a good degrease from the auto parts store then rinse it off. Cover the windows with packing paper and masking tape. Cover the lights and reflectors with masking tape.
If you want the 3 color camo, check out the painting manual, 43-0209. I found it helpful to print out the pages and color then in with colored pencil. Paint the whole truck green and let it dry. Then paint the black and brown. I used rattle cans for the black and brown. Rapco is good paint.