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