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