Simichrome is probably the best metal/plastic polish around. I use it on everything, even used it to clear up some plastic headlight covers that had gone yellow on my old truck.
Caswell offers a $20 kit that contains all the bits you need to remove the blue from your pipes. I have this kit and it works very nicely:
Here's the direct link:
http://www.caswellplating.com/buffs/bluejob.html
