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