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