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