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