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