If you want to learn about paint that was used in the automobile industry in the 1950's through the 1960's read the following article about automobile paint as used by Fender guitars. It might be more information that you might care to have, but for those that are seeking the correct color for their cars, it is educational. It explains the relationship of the color of the primer to the final color of the paint, and much more. Plan on spending about an hour to read it.
http://home.provide.net/~cfh/fenderc.html
http://home.provide.net/~cfh/fenderc.html