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)(11,16)(12,24)(13,27)(14,18)(15,19)(17,30)(20,36)(21,35)(22,25)(23,32)(26,29)(28,40)(31,38)(33,37)(34,39) involution — undirected(2,5)(3,7)(9,11)(10,16)(12,25)(13,28)(14,21)(15,23)(17,33)(18,35)(19,32)(20,29)(22,24)(26,36)(27,40)(30,37)(31,34)(38,39) involution — undirected(9,12,14,10,15,18,24,19)(11,16,22,25,23,32,21,35)(13,26,29,17,30,34,39,27)(20,31,28,33,38,36,37,40)(2,5)(6,8) involution — undirected(1,3,4,7)(2,6,5,8)(9,13,24,39,15,30,14,29)(10,17,12,26,19,27,18,34)(11,20,21,37,23,38,22,28)(16,31,35,40,32,36,25,33)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.