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