The article explains the Call Screen in the Tango Tango app for iOS and Android.
Anytime the app is in a PTT call, the Call Screen will be shown.
The state of the PTT button is indicated by its color and is determined by the state of the call.
Green: The floor is available. Press PTT to take the floor and begin talking.
Red: You have the floor and may speak on the call.
Grey: Another user has the floor.