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