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