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