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