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