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