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