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