the color of the under coat primer, next to the metal shouldn't change the color.
the product that will change the color is the sealer coat you spray on before the top color.
i would check with the person spraying the color to determine what color you should use as sealer.

on another note. you shouldn't using PPG primer under a DuPont system.
i know i will be flamed by many saying they cross product materials without problems. but for maximim performance of the paint, and the ability to warranty it. you should use the same product brand from primer to top coat.