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