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)(11,17,18,24)(12,20,22,15)(14,21,23,19)(25,26,29,32)(27,33,35,40)(28,36,38,31)(30,37,39,34)(2,5)(6,8)(11,18)(14,23)(17,24)(19,21) involution — undirected(1,3,4,7)(2,6,5,8)(9,11)(10,14)(12,21)(13,18)(15,24)(16,23)(17,20)(19,22)(12,22)(15,20)(17,24)(19,21)(25,27,29,35)(26,30,32,39)(28,37,38,34)(31,40,36,33)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.