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