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