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