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