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)(11,15)(12,13)(14,16)(17,18)(19,24)(20,21)(22,23)(25,26,30,31)(27,29,33,38)(28,32,37,39)(34,36,35,40)(1,2,4,5)(3,7,8,6)(9,11)(10,14)(12,15)(13,16)(18,23)(19,21)(26,31)(29,38)(32,39)(36,40)(2,5)(6,7)(11,16)(14,15)(17,19,22,21)(18,24,23,20)(25,27,30,33)(26,29,31,38)(28,35,37,34)(32,40,39,36)(1,2)(3,6)(4,5)(7,8)(9,11)(10,15)(12,14)(13,16)(17,20,22,24)(18,19,23,21)(25,28)(26,32)(27,34)(29,36)(30,37)(31,39)(33,35)(38,40)(1,3,4,8)(2,6,5,7)(9,12,13,10)(11,14,16,15)(17,21,22,19)(18,24,23,20)(25,29)(26,33)(27,31)(28,36)(30,38)(32,35)(34,39)(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.