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