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