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