Green or yellow does indicate an infection. If it is due to a sinus infection antibiotics will not work for that is a viral infection. If it's been more than 2 weeks then it may be something else, if it has only been a few days then it is something you have to wait for it to clear up on it's own. You don't want to give a child antibiotics if they don't need them along with an infection that is not curable with antibiotics.
Just make sure your child drinks plenty of fluids at this point and gets plenty of rest.
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