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