Oxygen has a strong green emission, so gases rich in oxygen may appear green, which is why many nebulae are green, like also most auroras in the Earth's atmosph

Oxygen has a strong green emission, so gases rich in oxygen may appear green, which is why many nebulae are green, like also most auroras in the Earth's atmosphere. Therefore indeed a star behind gas rich in oxygen may appear green, but that green light comes from the gas, not from the star.