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