Just had a look at a load of pics Vaughan, B&W and colour. On bare metal P-47s, the hinge line of the flaps seems to be bare metal, with the ends in ZC, and on camouflage aircraft, the hinge line is the upper camouflage colour, with the recess in the wing in laquered bare metal, and the ends of the flaps ZC. The Duxford example shows this (for a camouflage example), and the IWM are normally fastidious at getting details right.