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