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