RealGM

What do they mean?

Radio-equipped helmets.

They're usually on QBs I think

You're only allowed to have one radio helmet on the field at a time, so they have to mark which one that is. It's a result of the like two plays Vick and Schaub were on the field at the same time last year, both with radios.

I swear I saw Brian Westbrook of the Eagles wearing a green sticker. So, if only one radio equiped helmet is allowed, does that me that the coaches communicate with Westbrook and then Westbrook tells McNabb the play? That just seems weird to me.