Here are a few links that you may find useful and that may come up during the discussion:
- Jorge Capestany's video explaining the logic and physics behind the use of different balls for different players.
- International Tennis Federation (ITF) endorsement of ROGY.
- USTA's suggested competencies for the various ball colors.
- 10andUnderTennis site
- The facilities where I teach using these formats: Lexington County Tennis Complex and Cayce Tennis and Fitness Center.
- An Australian study comparing yellow vs green balls during high level 9-10 year-old player matches