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