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