Yes, session links can visually appear differently for internal purposes. However, all can still be used to join a session. Old links will still work and are not affected. To confirm, previously created sessions/links are not affected and can still be used by any guest who has one.

The Share Link can be used as many times as needed to use one session for recordings effectively. This article has more info on the ways to invite guests as well: Invite Co-Hosts & Guests to a Recording Session.