Why didn't Colby understand anything that was said in Chinese? He was a double agent for the Chinese government, after all. Shouldn't he be able to speak and read the language? Granted, I don't think they said if people were speaking Mandarin or Cantonese, but I'd expect that he'd have to have known both for the covert work he was doing. Or at least have a throw away line that they were speaking the dialect he didn't understand, if he only knew one. (Unless they did and I missed it.)
It was careless of them to not acknowledge that part of his past. Yes, I can understand wanting to put that part of his past behind him, but it would have been useful in this case.
P.S. Look, I finally got some non-Charlie icons! There's a Don in my userpics now too.