Motorcycle exhaust bluing is a pretty common problem for bikers. Usually it can be an indicator of a problem with the bike’s engine not running at optimal conditions. Motorcycle exhaust bluing is caused by excessive heat which is usually caused by the engine running lean which makes it run hotter then normal and therefore the pipes on a bike will heat up excessively as well. This over heating will cause the metal that exhaust are made from to start turning a bluish color. You can buy a cleaning agent and remove the bluing however unless you solve the problem of the engine running hot its just going to come back.
To permanently stop motorcycle exhaust bluing inspect the exhaust system for any leaks at where the system meets the engine. If everything looks fine then its time to take the bike in for a tune up or an inspection by a motorcycle mechanic in order to resolve what might be causing the motor to run hot. Motorcycle engines tend to run hot however when the heat is causing bluing their is generally a problem with the motor getting excessive air which causes it to run hotter than it should.
If you switched to an aftermarket motorcycle exhaust systems on your bikeand did not have the computer remapped to accommodate the new system that might be all that is needed. As a general rule it is always a good idea to have your bike re tuned when you switch out the stock exhaust for an aftermarket system or even just replacing the mufflers will make the bike run different.