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