Simichrome has been around for years and years... It is a polish containing 8-10 micron abrasive. There are a few more agressive polishes available, but I have always used Simichrome.... maybe more work, but I'm not afraid of damaging the finish.
If your pipes have actually gone "blue", a power tool is called for. Either remove the pipe and use a bench grinder with a buffing wheel, or get a small air grinder with a buffing wheel and do it on the bike. It has been my experience that once the pipe changes color, you can get most of the discoloration off, but it will come back again.
To do this by hand with Simichrome and a rag, once it has "blued" would take hours and gallons of sweat...
