Online research tells me the primer was red then base coat of dark yellow.I want to try "hairspray" method.I see most people use a black primer before basecoat.Should the primer be black or red?At 1/35 scale would red be more noticeable then black primer?Am I correct to assume black represents the steel before the red primer coat?Would a combination of black and more rusted area's with red be good?Thanks.

Guys put down black primer to pre-shade the model. It has nothing to do with anything on the actual tank. If you plan to chip and want to show primer - then you should have a coat of red oxide under the dark yellow. Unless the vehicle is from Daimler. They used zinc oxide primer - which is an 18% grey.
Oh, and welcome to Armorama!