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