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