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