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