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