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