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