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