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)(13,15)(17,20)(18,21)(19,22)(23,24)(25,26)(27,35)(28,31)(29,38)(30,33)(32,36)(34,39)(37,40) involution — undirected(2,5)(6,8)(9,11)(10,14)(12,18)(13,17)(15,20)(16,21)(19,23)(22,24)(25,27,29,28,30,36,39,37)(26,31,34,35,33,40,38,32)(1,3,4,7)(2,6,5,8)(11,17)(14,20)(18,23)(21,24)(25,28,29,36,30,37,39,27)(26,32,34,31,33,35,38,40)(10,15)(14,20)(16,22)(21,24)(26,33)(27,36)(28,37)(34,38) involution — undirected(9,12,13,19)(10,16,15,22)(11,18,17,23)(14,21,20,24)(27,36)(28,37)(31,40)(32,35)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.