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