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