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