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