Red bell peppers are simply ripened green bell peppers. Green bell peppers are harvested earlier, before they have a chance to turn yellow, orange, and then red. As a result, they are the least sweet of the peppers and have a slightly bitter flavor. Red bell peppers are the sweetest. They also have significantly more nutrients than green bell peppers as they are harvested later.u003cbr/u003eRoasting green bell peppers gets rid of the bitter flavor and makes them sweeter.