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