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