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