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