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