ANSWER
Some traders wear an "X" on certain places on their clothing to mark areas where they have been injured. Frequently the tape is red, and in the form of a cross, as in a "red cross". With all of the activity on the trading room floor traders frequently bump into each other, or worse. Traders will try to avoid contacting a place marked with an "X", although there are no guarantees.
WHO GOT IT RIGHT: John Trotter, and Kathi Reynolds.
