Why are orange bell peppers more expensive? There are two reasons, one is while the other one just involves ripping you off. Because of the health benefits associated with colored (non-green) peppers, supermarkets know that customers are willing to pay more for them which is part of the reason they cost more. It's certainly not a fair reason to charge more as it should be less expensive to eat healthy, right?
There is one valid reason though for the price difference and that is orange peppers being more perishable. This is because they are picked when nearly ripe, while green are picked very early. Since the orange variety is almost ripe when it leaves the farm for the store, it's not able to sit on the shelf as long. It's understandable why stores have to charge more for that aspect, since it gets more easily bruised and tarnished and therefore, often times more of the brighter colored peppers need to be discarded by the store instead of sold to customers.
In terms of their antioxidants, the ORAC values of all colors - green, red, yellow, and orange - are surprisingly very close.
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010