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)(25,26,30,32,28,33,29,34)(27,35,38,40,36,31,37,39)(1,2)(3,7)(4,5)(6,8)(9,11)(10,14)(12,18)(13,19)(15,22)(16,17)(20,23)(21,24)(25,27,28,36)(26,31,33,35)(29,37,30,38)(32,39,34,40)(2,5)(6,7)(26,32)(29,30)(31,39)(33,34)(35,40)(37,38) involution — undirected(9,12,13,21)(10,15,16,20)(11,18,19,24)(14,22,17,23)(25,27)(26,31)(28,36)(29,37)(30,38)(32,39)(33,35)(34,40)(1,3,4,8)(2,6,5,7)(11,19)(14,17)(18,24)(22,23)(26,33)(27,36)(32,34)(37,38)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.