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