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