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