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