Don't even bother yourself about the brown headers, Matsuke. That is normal. Mine were purpley brown by 200 miles. They might look bad but That surface corrosion isn't going to rust through. Mine were solid as new after ~12,000 miles even though they were discolored. There was no problem removing header nuts. It looks pretty rusty but it really could be called an thinly oxidized patina more than a true rust film.
I do not think there are a lot of bikes that will retain a like new look to the header. I was once told that there was a Honda manufactured that had headpipes housed within a chrome pipe. The real pipe on the inside looked like crapola but it stayed nice and shiny on the outside because that was actually a false pipe you were looking at.
08 MIDNIGHT SAPPHIRE BLUE ZX-14 Now Deceased, will be resurected
2024 ZX-14R bran friggin NEW!