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