Anyone can find single examples of anything by searching for words or phrases on the internet. The ability to show single isolated examples doesn’t prove that usage is common. The use of the word “colleagues” is not common among everyday working folks. Most of the people posting here have at least one university degree, and many have several, and many have medical degrees or work in and around universities or medical schools etc. where the term is more common. But it’s not street language. I know this from living in the real world, as opposed to spending my entire life in schools, as you doubtless have from elementary through high school to undergrad to med school to specialization in psychiatry to your current position at the University of Toronto. I have spend a huge portion of my life relating to small businessmen, tradesmen, hotel bellhops, factory workers, non-credit continuing ed. students from all walks of life, etc. I haven’t heard them talking about “colleagues” very often. You won’t convince me by quick lookups on the internet that what I know from 60+ years of personal observation (probably 20-30 years longer than you’ve been alive) is false. And it’s a sign of how easily you are distracted from substantive issues that you’d invest precious time quarrelling about a word I used only in passing in response to something else.
I want confirmation from a dozen sources other than John Harshman. Can you provide them, or not? If not, I suggest you sit out and let people with knowledge do so. Author, title, date, page numbers, please.