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