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