Gray or Grey?

My six-year-old grandson plays soccer in Ringgold.  His team has gray jerseys, so at last Saturday’s game everyone was yelling, “Good defense, Gray!” and “Get the ball, Gray!”, and “Guard the goal, Gray!”  Of course, Greyson thought everyone was cheering for him personally.  But then they were yelling at him personally as well.  His coach was telling him one thing to do, but everyone was yelling at him to do something else.  Gray’s dad explained the confusion at half-time, so Grey knew what was going on for the second half.  At least I think he did.