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