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