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