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