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