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