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