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