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