One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,6,8)(3,5,7,4)(10,16)(11,20)(12,15)(13,27)(17,33)(18,28)(19,25)(21,36)(22,29)(23,38)(24,37)(26,30)(31,35)(34,39)(2,3)(4,5)(7,8)(9,10)(11,21)(12,25)(13,28)(14,19)(15,16)(17,23)(18,30)(20,35)(22,34)(24,31)(26,32)(27,40)(29,36)(33,37)(38,39) involution — undirected(1,3,5,8,6,7,4,2)(9,11)(10,17,19,21)(12,24)(13,29)(14,23)(15,22)(16,31,25,34)(18,36,28,33)(20,27)(26,38)(30,37)(32,35,40,39)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.