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