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