Tsull, the first picture of a Panther you posted has to be completely ignored this is not a G model it is in fact the Panther II mated with a G turret, the tank was captured without a turret fitted this was added at a later date and completely painted some years latter this picture was taken, Panther II was only ever a prototype.
As for shades of red oxide even today we can get different shades from the same factory depending on batch and date supplied during the war this was exaggerated to a much higher level so we see shades from almost red to almost brown and everything in between, the rear of the Stug you have to be careful with as some German units used red outlines on the Balkan cross and divisional markings this wouldn’t be red oxide primer