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