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