One vertex per element, one color per generator, with an edge from x to x·s.
(1,2) involution — undirected(3,4,5,6)(7,8)(9,17)(10,14)(11,24)(12,16)(13,20)(15,18)(19,32)(21,33)(22,31)(23,30)(25,29)(26,37)(27,34)(28,35)(36,38)(7,9,18,34,12,21,11,20)(8,13,24,33,16,27,15,17)(10,19,22,35,23,36,25,37)(14,28,29,32,30,26,31,38)(7,10,18,22,12,23,11,25)(8,14,24,29,16,30,15,31)(9,19,34,35,21,36,20,37)(13,26,33,38,27,28,17,32)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.