1955 Model D150 - Cylinder and cylinder head colour

The cylinder on this model should apparently be painted matt black (like the silencer), but the cylinder head always shows as silver/aluminium.
Was it left as bare aluminium from the factory, or was it painted (in Fiat 690 silver colour to match the engine perhaps) ?
V.T's Restoration Guide is silent on this, but the black and white picture clearly shows the colour difference between the cylinder and the head.
Was it left as bare aluminium from the factory, or was it painted (in Fiat 690 silver colour to match the engine perhaps) ?
V.T's Restoration Guide is silent on this, but the black and white picture clearly shows the colour difference between the cylinder and the head.