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