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