If by 'Red' you mean Mulberry, then I'd go for that. Unless by 'Tan' you mean 'Saddle Brown' in which case I'd probably go there.
I wouldn't worry about retaining factory originality, as JCK says, it's your car, so have it the way you want rather than how somebody 50 years ago thought it should be. It's not like there were any specific colour combos designated by the factory, people had whatever they wanted.
