Each group of four players in a scramble has a yellow ball (or pink, or a white ball that has been marked) that rotates among players. For example, Player A uses it on the first hole, B on the second, C on the third, D on the fourth, then back to A on the fifth and so on.
In this game, two scores per hole are added together for the team score. Here's the catch: One of those two scores must be from the player with the yellow ball. So on each hole, the team score will be the score of the player with the yellow ball, plus the lowest score of the other three players on the team.
Does the ball actually have to be yellow? Of course not, but the ball should be marked in some way to designate it as "the" ball.
There are a couple variations that add to the tension of the game. In one, if the player playing the yellow ball loses it, that player is eliminated from the game. The group would continue as a threesome with a new yellow ball.
In another, if the yellow ball is lost, the entire team is eliminated from the competition. Pretty harsh.
And in another, the yellow ball serves as a "bonus" competition. The 4-person teams compete using the two low scores on each hole; the yellow ball score is kept separately. The team with the lowest yellow ball score wins a bonus prize.

