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)(11,14)(12,19)(13,16)(15,21)(17,24)(18,23)(20,22)(25,26,31,33,30,29,28,37)(27,32,36,39,34,38,35,40)(2,5)(3,7)(9,11,13,18)(10,14,16,23)(12,20,21,17)(15,24,19,22)(26,29)(27,34)(33,37)(35,36)(9,12,13,21)(10,15,16,19)(11,17,18,20)(14,22,23,24)(25,27,31,36,30,34,28,35)(26,32,33,39,29,38,37,40)(1,3,4,7)(2,6,5,8)(10,16)(14,23)(15,19)(22,24)(25,28,30,31)(26,33,29,37)(27,35,34,36)(32,39,38,40)(2,5)(6,8)(25,29,31,37,30,26,28,33)(27,32,36,39,34,38,35,40)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.