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