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