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