One vertex per element, one color per generator, with an edge from x to x·s.
(1,2) involution — undirected(3,4,6,5)(7,8)(9,18)(10,23)(11,16)(12,27)(13,17)(14,21)(15,26)(19,33)(20,29)(22,32)(24,38)(25,30)(28,34)(31,36)(35,37)(3,5,6,4)(7,9,12,21,13,22,11,20)(8,14,16,18,17,29,27,32)(10,19,25,35,26,36,24,34)(15,28,30,31,23,37,38,33)(7,10,12,25,13,26,11,24)(8,15,16,30,17,23,27,38)(9,19,21,35,22,36,20,34)(14,28,18,31,29,37,32,33)(7,11,13,12)(8,16,17,27)(9,20,22,21)(10,24,26,25)(14,18,29,32)(15,30,23,38)(19,34,36,35)(28,31,37,33)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.