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