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