Imagine you are at a boring meeting and you want to signal to a friend that you want to leave with him. You can flash him a yellow light. If he flashes green in return then you can both run to the door.

Or

Imagine you are at a bar a would like to talk to a girl you have been staring at for the pass few minutes. Flash her an amber light to signal that you would like to chat with her. If she flashes a green light then you know she is interested too. If she flashes a Red light then sorry mate on to the next one. Those are 2 ways of using this app,, but there are more uses, like 2 students in a classroom, in place of texting may use this communicate. Be ingenious.