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