Who called that play, the coach or the quarterback? Fans and commentators may not be able to tell!

The green spot indicates that the helmet is equipped with a speaker that allows the player to hear signals or communications from the team coaches. Only one offensive player (quarterback) and one defensive player (linebacker usually) is allowed to have such communication at any one-time on the field of play.

The communication is only one way (from the coaches) and is allowed only until the 15 second mark prior to the start of each play.

This type of communication is not permitted in the college football rules.

More Info: www.nfl.com