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