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