Over at another forum there is a perfect example of why you ALWAYS intermix cans of paint. If you order up enough paint for your project and it is in more than one can, don't assume they were mixed properly, don't assume anything! Get another new, empty can if you must, and use it to intermix the cans of paint you have to be SURE they are the exact color.
This fella made a very common mistake, he trusted the paint store. I did the same thing once, which was my first lesson on the subject. It is an easy fix in his case and he will keep right on rocking. But it could have been a disaster.
Different shades of white purchased and mixed at the same time.
Here is a "Basics of Basics" on painting a car in pieces.
Spraying - Autobodystore