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