Green phlegm is usually a virus. With the flu, there is usually more body ache and a fever up to 102 degrees F. Colds often have more runny nose and sneezing. There can be a little body ache, but it's not so much you desperately want to stay in bed or return there if you forced yourself to get up.
For a cold take zinc gluconate (it has to be gluconate) tablets, 50 to 75 mg. I don't recommend the lozenges because there is sugar and you don't want sugar when you're sick).
For both, chicken soup and Advil are helpful.
I have a cold right now myself. This one started with eye itching, or else I got it because my eyes were itching and I couldn't keep from scratching at the tear ducts. Zinc and Advil are making it bearable. If nose runs too much or there is too much sneezing, I'd consider an antihistamine,I think decongestants are worthless.
If it's a cold, then it would disappear in a few days and if not then it's most likely flu or something else. Just take paracetamol for the aches and pains and try some vapour rub to help clear congestion. You say that you were coughing up green stuff though? I would keep an eye on that, if you're congested and coughing up green stuff that's usually sign of infection because it should be cloudy white or clear otherwise. If it continues go see your doctor.