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