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