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