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