The correct answer is option 3, Uranus. Uranus is known for its unique blue-green color, which is due to the presence of methane gas in its atmosphere. Methane absorbs red light and reflects green and blue light, giving the planet its distinct color.

Option 1, Jupiter, is not the correct answer because it is predominantly covered in clouds and does not emit a specific color of light.

Option 2, Venus, emits a yellowish-white light, not green.

Option 4, Neptune, is often described as a deep blue or azure color, rather than green.

Therefore, the correct planet emitting green light is Uranus.