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