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