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