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