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