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