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