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)(11,12,17,16)(13,21,22,18)(19,23,24,20)(25,26,30,31)(27,28,32,36)(29,37,38,33)(34,40,39,35)(1,3,5,8)(2,6,7,4)(10,15)(12,16)(18,21)(20,23)(25,27)(26,28)(29,34)(30,32)(31,36)(33,35)(37,40)(38,39)(1,2)(3,4)(5,7)(6,8)(10,15)(11,17)(13,22)(20,23)(26,31)(27,32)(29,38)(35,40) 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)(25,27)(26,28)(29,34)(30,32)(31,36)(33,35)(37,40)(38,39) involution — undirected(1,3)(2,4)(5,8)(6,7)(9,12,14,16)(10,17,15,11)(13,20,22,23)(18,24,21,19)(25,28)(26,32)(27,31)(29,35)(30,36)(33,39)(34,37)(38,40)(1,4)(2,3)(5,6)(7,8)(9,13)(10,18)(11,19)(12,20)(14,22)(15,21)(16,23)(17,24)(25,29,30,38)(26,33,31,37)(27,34,32,39)(28,35,36,40)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.