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