I remember reading somewhere that GW at the time still outsourced their plastic production. Apperently they where cast by a company that made the plastic interiors of Matchbox toy cars. So the colours where those you'd find inside 1980's toy cars.
Resin 3d printing is the way to go. I had some oldhammer stuff printed and the details are really good. No need to pay £20,00 for one vintage renegade marine if you can print them.