You need to speak or chat with someone asap, their status is red or yellow, you would like to get a pop-up notification when their status turns green and they become available

In MS Teams in the Chat column, hover over a name, click on the 3 dots,  click on Notify When Available.

You will continue to get notifications whenever that person becomes available, forever until the end of time, until you turn it off.  

In the Chat column, hover over a name, click on the 3 dots,  click on Turn off notifications.  

This is such a good PROTIP, that all the other PROTIP's think it's a PROTIP.  You are now a master of time and space, able to bend time or space or both to your will.  Credit goes to Daniel Larese for teaching me this one.