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