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