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