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