Add the remaining 1 teaspoon oil to the pan. Add shallot and cook, stirring often, until softened, about 1 minute. Add the reserved grapefruit juice and vermouth (or wine) and bring to a boil. Boil until reduced by half, about 3 minutes. Reduce heat to low and add honey, the grapefruit sections and mint. Return the scallops to the pan and reheat gently, turning to coat with the sauce.