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