A senior colleague should will interact with you in some ways that are similar to how your supervisor would. That's why there is a distinction of "senior". Wh

A senior colleague should will interact with you in some ways that are similar to how your supervisor would. That's why there is a distinction of "senior". What exactly that relationship looks like is up to you and your supervisor to determine. Can he task you directly? Are you required to provide him updates on your work? Is he involved in your performance evaluation? Etc.