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