Google is making it easier to see who is available for a Hangout with a new Contacts tab. The new tab will show first a list of available contacts (green circle) in alphabetical order followed by a list of unavailable contacts in alphabetical order. Contacts can also now be hidden or pinned to the top of your contact list regardless of whether they are currently available. We expect to see this change in the UMICH domain within the next two weeks.
For more information, see New available contacts tab for Hangouts in Gmail.