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