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