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)(11,16)(12,17)(13,18)(14,15)(19,20)(21,23)(22,24)(25,26,30,33)(27,34,28,31)(29,32,38,37)(35,40,36,39)(1,3,4,8)(2,5,6,7)(25,27,30,28)(26,31,33,34)(29,35,38,36)(32,39,37,40)(10,15)(13,17)(16,23)(20,24)(27,28)(31,34)(35,36)(39,40) involution — undirected(9,11)(10,16)(12,22)(13,20)(14,21)(15,23)(17,24)(18,19)(25,26)(27,31)(28,34)(29,37)(30,33)(32,38)(35,40)(36,39) involution — undirected(9,12,14,18)(10,17,15,13)(11,19,21,22)(16,20,23,24)(25,28,30,27)(26,31,33,34)(29,36,38,35)(32,39,37,40)(9,13,14,17)(10,18,15,12)(11,20,21,24)(16,19,23,22)(25,29)(26,32)(27,35)(28,36)(30,38)(31,39)(33,37)(34,40)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.