[AtlUmpSteve]

Sliding pants must match to minimize the liklihood of the pitcher being the only player on a team wearing a distraction at the release point (from the hip). Sliders are optional, and worn for a purpose; yet often seem to be part of team purchase.

Upper body undergarments are more often worn just for an individual's comfort with temperature, and is rarely part of a team purchase. It is less reasonable to mandate not wearing a garment when cold because it doesn't match. While it is true the pitcher might wear a distracting item on her pitching arm, that can be excluded with judicious use of the rule; yet, still allow the pitcher to wear a different color undergarment, instead.