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)(9,13)(10,14)(11,12)(15,21)(16,19)(17,22)(18,20)(23,24)(25,32)(26,36)(27,31)(28,30)(29,35)(33,38)(34,37)(8,12)(13,19)(14,20)(21,22)(23,25)(24,29)(26,34)(27,35)(28,33)(30,37)(31,32)(36,38) involution — undirected(4,6)(7,9,11,16)(8,13,12,19)(10,17,18,15)(14,22,20,21)(25,33)(26,28)(29,37)(30,36)(32,38)(34,35)(7,10,11,18)(8,14,12,20)(9,15,16,17)(13,21,19,22)(23,26,27,28)(24,30,31,36)(25,34,35,33)(29,37,32,38)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.