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