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