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