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