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