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