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