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