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