My hair has a green tint, but I didn't dye it?

I just noticed that towards the end of my hair there's a greenish tint. I do not dye my hair, I do not go swimming, and I never (that is not an exaggeration) let the sun touch (that's the wrong word, lol) my hair. I take really good care of my hair, I only wash it every 3 days and I even started taking omega-3 (or is it 6?). I see no possible reason why my hair should have this green tint, so why? My hair is a dark shade of brown, and almost 2 feet long, if that changes anything. Thank you for your time.