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