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