The process is like Jack says--here is a link to a company which can do this (but the local jobber can do this too)
http://www.tcpglobal.com/autocolorlibrary/aclchip.aspx?image=1953-kaiser-pg01.jpgIf you adjust the info in the URL in your browser, you can see just about anything that is available, like 1963-Studebaker or 1956-Nash etc. These chips online are just a vague approximation of the real colours, due to fading, and computer screen colour limitations, so the special vault chip scans and the other proprietry formulae information is what is needed, not the physical chips you can buy off Ebay
Getting the colour match just right is not only based on having the right combination of pigments in the correct amounts, but also correcting for other factors, such as the size of metallic flakes (which has changed over time!) and also for the different paint in use. The black of a 60 Studebaker Hawk's original paint is vastly different in depth, gloss and overall look from a modern black, which is far too hard and glossy, and not anywhere near as 'velvety' at all.