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