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