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