Chipping color on Kriegsmarine vessels

[Thegreenmachine]

Hi,

I'm currently working on a 1/72 scale Bismarck turret depicting her after the final trials. Since the scale offers much in the way of weathering possibilities, I'm tempted to add some minor paint chipping on some areas - but I'm not sure which color to use. What was the basecoat underneath the grey paint? Red oxide paint (german "Menninge")? Or just a dull darker grey tone? I've decided to avoid any hard rust staining, as the ship was rather new at this point and rather well kept by its crew. But I guess the training and harsh conditions in the baltic sea during winter had some effects on the paintwork...