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