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