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