Class sash
From AmtWiki
A class sash is an identification method so that players can easily determine another player's chosen class. The color indicators can be found in the Rulebook.
Garb Requirements
Version 7.5 Page 13, Rule 12
For the purpose of determining what class people are playing, class sashes must run diagonally across the chest from one shoulder to the opposite hip. They must be at least two inches wide. You may not wear sashes for classes you are not currently playing.