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