Everybody has something to say about colleagues and talking about them can help get students talking about more personal things, which can really help them exit their comfort zones. A few good questions could be:

What do you think about your colleagues?

What are some common problems with colleagues?

Have you ever had any challenging situations/altercations with your colleagues?

Do you spend time with your colleagues outside of work? Why/why not?

Who is your favorite colleague? Why?