You return from open sea. You see a green lighted buoy with a number 3. What should you do

Green markers will always have an odd number on them. If you are heading upstream it should be to your left. If you are heading downstream it should be to your right. It will be opposite a red marker or bouy with an even number on it. To aid in navigating, the term "red, right, returning" is used meaning as you return from open waters (head upstream), the red marker, bouy, sign etc, should be to your right. That means the green one, in your example with a 3 on it, should be to your left. If its on your right side, you are outside the cleared channel area.