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