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