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