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