Ask your colleague what they want you to do. Source: The speech therapist I took my son to today for his first appointment. I asked the therapist the same exact questions. A little more: It's important for people who stutter more when they are in particularly stressful situations to feel confident and in control. Your colleague is in a much different place than my son, but he/she was comfortable talking to you about it right from the start, so it's really ok to ask. It's ok though. Nobody is born knowing this stuff. I'm sure they'll appreciate you asking and you won't feel awkward about what to do either.