No hard and fast rule but a yellow primer under red gives it a bit more oomph.
The only 'not essential' but necessary rule is if the top coat is anything other than black or metallic the primer should be light, Grey or white.
I only ever use Humbrols matte, White, Black, Grey, or yellow as a primer coat, (depending on the top coat naturally, in some cases of course recently I'll use Humbrol rust as a primer as on the Ducati exhausts)