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