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