I've had issues with Tamiya paints before, more specifically the metallic/flourescents and the backing black bleeding through them. I stopped using Tamiya for various reasons, that being one. Anyways, even after 4 coats of the color on one body I had the black backing bleed though.
Last time I used Tamiya paints I did 2 coats of the color, backed by one light coat of metallic silver to give it a little extra pop and then hit it with black with no bleed through.
Typically, if you use a dark color, you'll back it with black, if you use a lighter color, back it with plain silver white. Using metallic silver/silver flake between the color and backing helps give the color a little extra pop, or a lot if you do a heavy coat.