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