Have you tried an antihistamine?
green and yellow flem should not be coming up from allergy unless it is stomach acid. Usually allergy is clear mucus. I'm not a doctor but I wonder if it is a bacteria infection. Sorry I don't know the correct answer. Maybe the doctors are correct too. I just personally haven't heard of colored mucus from allergy. Allergy can cause mucus that can lead to bacteria infection too. See another doctor.
i have had this cough for 2 months now and i would like to no that same question^^^^,when i cough it makes me vomit,and green and yellow flem comes out of my mouth i have been to the doctors and they have said its only hay fever or u have a lot of mucus , so they give me some tablets and the cough as not gone, i would like to what it could be and what could get rid of this cough i am really starting to worry now please some one right back