What do you think about it?

My father bought a black Z3 with a red soft top, red interior and a detailed (documented) history.
He bought it to re-sell it, but wants to swap/dye the interior and install a new soft top first, to get the car black/black.
He says the black interior would make the car more popular, I think he should keep the red interior (which is in like-new condition) so that the car stays the way it left the factory.

What do you guys think is the better way to go?