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