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