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