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