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