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