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