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