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