you cant...the pipes will always be that way...all your doing with that stuff they sell to remove gold and blue heat areas is going to sand your chrome off the pipes then when thats gone you will see dull nickle plating....
put heat shields over the area and they wont change color...All pipes will change color due to bad tuning,,,,and jetting of your fuel systm....Dont waste your money on re chrome...most Chome platers wont do used exhaust system due to all the carbon and junk in the pipes they cant remove....one set of pipes in there tanks could ruin the chemicals and that could cost $$$$$