No matter what base coat (grey or blue) under the black you put, the black will completely cover it up. I don't think there should be any difference at all. We used a navy blue base coat on my car since my car was grey, and the only reason we used the navy blue base was to cover up the grey (and also because it was a cheaper color than my royal sapphire pearl mix). In any case, no matter what is underneath, if it's painted right, your car will just be black, with any pearl on top of it. It will be hard to see the candy effect though. Stock preludes come with black with blue pearl, but you can hardly see it. If you want a candy paint, like Mike said, go with a lighter color such as white or silver.

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2004 WRX - WR Blue Pearl
1997 Eclipse GS - Royal Sapphire Pearl