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