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