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