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)(27,31)(28,36)(29,33)(30,34)(32,37)(35,38)(39,40)(1,3,4,7)(2,5,6,8)(10,15)(11,19)(17,21)(18,20)(25,27)(26,31)(28,33)(29,36)(30,35)(32,40)(34,38)(37,39)(1,2)(3,5)(4,6)(7,8)(10,15)(11,19)(17,21)(18,20)(27,35)(28,37)(31,38)(32,36) involution — undirected(1,3)(2,5)(4,7)(6,8)(9,11)(10,16)(12,20)(13,21)(14,19)(15,22)(17,24)(18,23)(25,28,30,37)(26,32,34,36)(27,33,35,39)(29,31,40,38)(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)(27,31)(28,32)(29,39)(30,34)(33,40)(35,38)(36,37)(9,13,14,24)(10,18,15,20)(11,17,19,21)(12,22,23,16)(25,29,30,40)(26,33,34,39)(27,36,35,32)(28,38,37,31)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.