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