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