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