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