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