Hi, Richard ~
Don't take small things like this too much to heart!
I also think "work colleague" is wrong because it's redundant.
~ "colleagues" refers only to professionals
~ "workers" and "workmates" -- used almost exclusively to refer to blue-collar work
~ "fellow workers" and "co-worker" -- used for non-professional white-collar work, but can also be used to refer to blue-collar workers
"At the University-wide Christmas party, the professor talked to his colleagues, while the secretary chatted with her co-workers. Meanwhile, the janitor hung out with his workmates."