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