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