You bet! Green tomatoes will turn red indoors as long as they have reached the critical color stage and have at least a dark green star on the blossom end of the fruit. In other words if they hit the ripen stage when green they will turn red on their own. If they are green and immature nothing will turn them red but the sun. If you leave them on the vine and bring indoors they get a tiny boost of ripening from still being attached to the vine. You can also wrap each green tomato in newspaper and let them ripen in a cool place. The trick is to keep the rotting tomatoes that do not ripen away from the good tomatoes so the brown rot does not spread. Even if frost hits before Halloween you can still enjoy red tomatoes for Thanksgiving - but rarely until Christmas unless you have a greenhouse. Keep growing, Marianne Binetti