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