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