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