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