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