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