Primer Color, what to use?

i have a dillema, what color primer do i use to get the "real" paint hue from acrylics? i only have a gray primer and a white primer.both tamiya.(the spray cans). i'm planning to use a OFF White ACrylic paint from Gunze, what color primer do i use to make sure i get the right Off white color?

and in any case, what color primer do i use for any paint hue to acheive the "real color"?

Hope you guys understand my questions, the answer may seem simple but i'd just like to hear the advice from the experts