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