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