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