From original painted steel wheels I have seen it looks like they painted the whole backside and the center of the hoop of the wheels black and then they painted the outside face with body color. Masking would have taken too much time so there should be body color overspray dusted on the inside hoop part that that tires cover up after they are mounted. Might be some overspray that falls thru the 4 slots in the face that ends up on the hoop inside where the brake drum or rotor sits too.