Final answer:
The libero's uniform in volleyball must be of contrasting color to the rest of the team to easily identify their unique role, as they are subject to different rules in rotation and actions.
Step-by-step explanation:
The libero's uniform in volleyball must be distinctly different in color from the rest of the team's shirts to make the libero easily identifiable to the officials, teammates, and spectators. The contrasting color helps distinguish the libero, who has unique rules regarding rotation and actions within the game. The Fédération Internationale de Volleyball (FIVB), which governs international volleyball competitions, requires this differentiation in the libero's attire.
This exception to the uniformity of team apparel highlights the libero's specialized defensive role; they are not allowed to serve, spike, or rotate to the front row in volleyball matches. Therefore, the contrasting uniform is essential for the quick recognition of the libero's permitted actions during play.