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