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