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)(11,15,16,13)(19,23)(21,24)(25,26,29,30)(27,33,34,31)(28,32,37,36)(35,39,40,38)(9,10,12,14)(11,13,16,15)(17,18,20,22)(19,21,23,24)(26,30)(27,34)(32,36)(35,40)(9,10)(11,13)(12,14)(15,16)(17,18)(19,21)(20,22)(23,24)(25,26)(27,31)(28,36)(29,30)(32,37)(33,34)(35,39)(38,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,10)(11,13)(12,14)(15,16)(25,27,29,34)(26,31,30,33)(28,35,37,40)(32,38,36,39)(1,3,4,7)(2,5,6,8)(9,11)(10,13)(12,16)(14,15)(17,19,20,23)(18,21,22,24)(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.