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