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