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