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