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