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)(26,28)(27,34)(29,37)(31,38)(35,39)(36,40) 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)(25,26)(27,31)(28,30)(29,33)(32,37)(34,39)(35,36)(38,40)(2,5)(6,8)(9,12,14,13)(10,16,18,17)(11,20,22,21)(15,23,19,24)(25,27,29,34,30,36,37,40)(26,31,33,39,28,35,32,38)(1,3,4,7)(2,6,5,8)(9,12,14,13)(10,17,18,16)(11,21,22,20)(15,23,19,24)(25,28,30,26)(27,35,36,31)(29,32,37,33)(34,38,40,39)(9,13,14,12)(10,16,18,17)(11,21,22,20)(15,23,19,24)(25,29,30,37)(26,32,28,33)(27,34,36,40)(31,38,35,39)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.