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)(22,24)(25,26)(27,31)(28,32)(29,30)(33,38)(34,37)(35,36)(39,40) involution — undirected(1,3,5,8)(2,6,7,4)(10,13)(14,16)(18,21)(22,24)(26,30)(28,35)(31,37)(33,39)(2,7)(4,6)(9,10,12,13)(11,14,15,16)(17,18)(19,22)(20,21)(23,24)(25,26)(27,31)(28,36)(29,30)(32,35)(33,40)(34,37)(38,39)(1,2)(3,6)(4,8)(5,7)(17,19)(18,22)(20,23)(21,24)(25,27,29,34)(26,31,30,37)(28,33,35,39)(32,38,36,40)(1,4,5,6)(2,8,7,3)(9,11)(10,14)(12,15)(13,16)(17,19)(18,22)(20,23)(21,24)(25,28)(26,32)(27,33)(29,35)(30,36)(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.