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