Always green
The green peppers that we are familiar with are types that are suited for either ripe harvest or un-ripe harvest. If these types are harvested un-ripe, they will quickly colour after harvest into a ripe stage, turning red, yellow or orange. In this ripe stage, however, they will taste just like a green pepper.
Sweetgreen, by contrast, is the first green pepper that stays green. Ultimately, the fruit does continue to ripen, but nothing changes on the outside. This property represents an enormous quality improvement throughout the entire chain. For supermarkets, for example, the loss percentage of green peppers is very low, and this means immediate cost savings.