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