Discoloration of chimney pipe

Hi all,
I finally fired my wood furnace for the first time this past weekend. It's a Woodchuck 2900 connected to about 30' of Supervent 8" class A stainless chimney pipe. I unfortunately got some wet wood that had been sitting outside under the edge of a roof, so I couldn't get a very hot fire going. My flue temp only reached about 200 degrees and I only had about three pieces in the firebox before I realized it simply wasn't going to burn hot enough to get a decent fire going. So, after about an hour or so I raked the pieces apart and blew the fire out rather than let it smolder all night.

A few days ago I was leaving for work and noticed my chimney pipe is now discolored at the top, right below the rain cap and only in this one spot. I took a picture this morning but the sun was just rising so it's a little dark...but I had to leave for work so it's the best I could do. The spot is maybe 6"-8" large and is bluish in color, the same type of blue you see when chrome is overheated. It doesn't seem to extend below the chase cap and I can't see anything inside the chase. What could have caused this? The fire only burned for a little over an hour and never was that hot...I can't see how there would have been enough heat way up there to discolor it like that. I'm going to pick up a couple cords of dry wood this weekend but I'm concerned about what this bluing means before I fire it again. Does this pipe normally discolor through normal use, or do I have other problems?

I don't remember if the wind was blowing that day. I don't understand how there could have been enough heat way up there to turn it blue. That was my main concern, I didn't think the outside of a class A insulated pipe should get that hot to where it would cause discoloration (assuming the heat came through from the inside). I've been gone to work all week during the daylight hours so I hope tomorrow I can get a better look at it.

I finally saw it today in better light. The only time before I was able to see it was in the morning when I left for work as the sun was just rising. The spot is on the west side of the pipe, so it was always darker on that side and it gave the illusion of the pipe being blue because of the direction of the sun. When I got home from work it was dark, so it wasn't until this afternoon I was able to view it in direct sunlight. It does look more like a soot stain, the blue appearance was apparently just an illusion because of the direction of the sun and time of day. Thanks for the replies.