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