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