Red grapes, like Chambourcin for example, will slowly start to turn from bright green to a deep, dark red. Some bunches will change quicker than others and certain grape varietals also take longer to change color and ripen, such as Cabernet Sauvignon and Petit Verdot. Not only will the grapes change color, this time frame is also when the grapes will naturally start to sweeten. White grapes also go through this process, although not as obvious or magical. Instead of turning another color, white varietals become translucent.