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