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