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