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