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