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