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