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