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