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