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