I am restoring a November 64 San Jose Mustang and have noticed that in pictures of other cars, especially 64.5 cars, the grill color is a silver/blue, and others are a darker, gunmetal blue. There are traces of the lighter blue on the backside of my grill and it is nowhere near the color of the grill paint I bought from NPD. My question is, did they actually paint the grills the lighter color on earlier production Mustangs, and change at some point to the darker blue? Which is correct for my November 64 car?