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