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