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