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