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