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)(11,19)(12,16)(13,17)(14,18)(15,21)(20,24)(22,23)(25,26,31,30)(27,32,37,40)(28,33,29,34)(35,39,36,38)(9,11,14,21)(10,15,18,19)(12,20,13,22)(16,23,17,24)(25,27,31,37)(26,32,30,40)(28,38,29,39)(33,35,34,36)(2,5)(6,8)(9,12,14,13)(10,16,18,17)(11,20,21,22)(15,23,19,24)(25,28)(26,33)(27,35)(29,31)(30,34)(32,39)(36,37)(38,40)(1,3,4,7)(2,6,5,8)(9,12,14,13)(10,17,18,16)(11,20,21,22)(15,24,19,23)(9,13,14,12)(10,17,18,16)(11,20,21,22)(15,23,19,24)(25,29,31,28)(26,34,30,33)(27,36,37,35)(32,38,40,39)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.