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