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