If you open up the Friends List or when starting private games, there is a status light next to your friends avatar. This light can have different colors depending on the current status of your friends:
- No light: Your friend is currenly not online
- Green light: Your friend is currently using the app (eg. playing a training game)
- Orange light: Your friend is currently waiting in a room for a game to start
- Red light: Your friend is currently playining an online game.