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