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