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