What color primer under Plum Crazy

SPI told me to use white primer under Viper Red to make it pop .
It is true that the color of the prier can affect the look of the topcoat.
I noticed just this AM that PPG '69 B3 Blue, on the can it says the formular was redone back in like 2005. I wonder is the metallic part is also different than the first version!?