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