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