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