In the past we have used helmet beanies and mesh scout jerseys for our scout teams. We haven't been completely happy with either one. The beanies were easy to put on, but fell off easily and got stretched out after a while. The practice jerseys stayed on, but were a pita when you wanted to change guys. Felt it killed the tempo of the practice at times.
We are two platoon so our offense is in White, Defense is in Black, All JV is in Blue, and Freshman are in Yellow and Navy. We look like a freakin rainbow out in practice, but doing this allows for ease of scouting. We will bring out a handfull of practice jerseys with the sleeves cut off and the neck widened for the handful of kids that we may use on both sides to scout.