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