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