Colleague / Fellow colleague
UsageColleague already expresses shared work or professional membership. Fellow colleague is usually redundant, though fellow can sometimes be used deliberately for emphasis.
Colleague
Use when
You mean a person you work with or someone in the same profession or organisation.
Example
“My colleague from Finance will join the meeting.”
Fellow colleague
Use when
Avoid the extra fellow in ordinary formal writing unless you deliberately want rhetorical emphasis on shared membership.
Example
“Replace 'my fellow colleague' with 'my colleague'.”
Quick check
fellow colleague, fellow colleagues
Usage note