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