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