Hi Bob
First id like to say that your worried about the blue covering the yellow what you can do is have it customed mixed where they add tonners to deepen or lightn the shade. As far as the color sanding gose if it was me id color sand the base and the clear since your your going with a metalic and then color sand the clear. Dupont hot hues has some beautiful colors bob and for 500.00 thats not bad.