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)(27,36)(29,38)(32,39)(34,37)(9,11,14,20)(10,15,17,18)(12,19,13,22)(16,23,21,24)(25,26,30,35)(27,29,36,38)(28,33,31,40)(32,37,39,34)(2,5)(6,8)(25,27,28,37,30,36,31,34)(26,32,40,38,35,39,33,29)(1,3,4,7)(2,6,5,8)(9,12,14,13)(10,16,17,21)(11,19,20,22)(15,23,18,24)(25,28,30,31)(26,33,35,40)(27,37,36,34)(29,39,38,32)(9,13,14,12)(10,16,17,21)(11,19,20,22)(15,24,18,23)(25,29,28,32,30,38,31,39)(26,34,40,27,35,37,33,36)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.