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