not sure what they use for pigment, but it helps to have a primer that fits w/ the top coat yer gonna use - light gray or something for lighter colors say, rather than 'red oxide' or such - means less problem makin the color coat cover - different color primers also work good during the sanding phase as "wear indicators"
my buddy shot the front of my 58 w/ a gray epoxy primer that had a cool greenish tint when I was first redoin it and it was dark gray, and I drove it the first year that way until the rest of the bodywork was roughed out, then we flew at sanding the whole thing
Bill
