Sorry to hear about the problems with the paint. Especially since that green shade looked perfect. The problem you encountered is that you can't polish metallic paints without applying a clear coat first. Doing so cuts into the paint layer and exposes the metallic particles, with the exact result that you experienced. The best thing to do it apply clear over the green, then polish the clear. Some paints are worse than others, and that shade of green really shows bared metallic bits. That's too bad, but the final paint job turned out great, and it's a good looking colour, too.