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