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