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