The Warrior in bone stock condition runs very lean. I've only heard of one other bike having the heat shield turn color. If it's still on warranty you might want to let the deale take a look at it.
It's a simple matter to bump up the ECU a couple of points to richen it up. It won't hurt anything and it'll probably run a little better. It's set up the way it is now to meet environmental regs.

 

Same thing happened to me after almost 6000 Km. I thought I overheated the engine running very slow for some time. Don't think it will never turn the natural color again [/emoticons/emotion-6.gif]
Could it be a 950rmp idle speed too high?

Thx for the ECU tip, hope my Yamaha dealer can do it.

 

Is it possible to separate heat shields from the exhaust tubes? I could sand paint the shields.

 

get some fletz or blue away it will take the yellow out with a lot of rubbing with paper towls.