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