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