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