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