There was footage a few years ago with Ryan O. I forget what Survivor he was on; I think the one in Panama where they all had to jump off the boat in the clothes they were wearing, so most of the guys ended up in their boxers for the season.
Anyway, the footage was of Ryan O. racing in a challenge in his boxers, and his cockhead popped out of the fly of his boxers for a split second. How it made it passed the censors, I don't know, but the footage had the slow-mo replay, and sure enough, there it was. Quite average in appearance.
That was quite the season... the first episode had three guys on one of the teams stripping naked to drag a cart through the jungle or somesuch. One guy's boxers kept sliding down, so he just ended up removing them, and some of his male teammates did the same as a "sign of unity." :evilgrin:
As for Colby, I believe bulgereport.com mentions his masturbating at night during his Survivor season. However, I do not have a membership. I believe DoubleMeatWhopper, here on the forums, has/had one, as he mentioned a previous question about another celebrity. Maybe he can do so again.