How should the shirts of referees be styled according to the requirements?

Shirts worn by referees must be styled in a manner that is both professional and standardized for easy identification during matches. The correct answer indicates that referees can wear either long or short-sleeved shirts, which allows for comfort and consideration of different weather conditions while ensuring uniformity. The requirement for a state-approved color maintains a consistent appearance that reflects the officiating standards expected in volleyball, thereby contributing to the overall professionalism of the sport. This flexibility in sleeve length along with the stipulation of an approved color helps create a cohesive look among referees, ensuring they are easily recognizable while officiating.