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