There could be a couple of reasons why pesto gnocchi isn’t vibrant green in color. 1. You used store-bought pesto that isn’t fresh and vibrant green in color. 2. You overcooked pesto and cream sauce. Remember do not boil the sauce, allow it to just heat up. 3. Pesto gnocchi when stored for a long time, will oxidize and turn brown. Always serve pesto gnocchi immediately for the best taste.