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