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