Sound deadner/undercoating in the trunk?

I am working a 69 Mach1, getting it ready for paint. In my car the deadner/undercoating on the inside of the rear 1/4's is black with the factory color under it. This car has been painted before but I highly doubt that it has been painted inside, very cheep job previously! I have looked at many cars at shows & I see both the deadner/undercoating painted body color & black. Which is correct?

My car is an SJ car that has spent all of it's life in north TX, as far as I know.

Mike