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