What is a green carburetor to you ? Well  not idle when running or will not start  try to start  but this is a new unit . And why would this happen? It had fuel in it for a long time just a little bit not much at all to see if the Engine would run off the manufacturing line. Then  all fuel is drained out and the unit will go off to shipping.   Sitting in a warehouse sometime up to a year this can't be helped by anyone  . But one thing that might happen is Corrosion in a light green fluffy powder .The Main jets are made out of brass just like a brass ring on your finger it will turn green in time . Carburetor can be repair and clean up to work like its a post too. I do this all the time here in my shop and some carburetor can't be repair been sitting way to long in there garage . Or out side not cover up from the weather i have carburetor ship in for repair and i can tell its been out side sitting to long time, not being run ones a month to let new fuel come in side the carburetor bowl . Way it helps to keep your carburetor clean.   The fuel breaks down from time setting around inside your carburetor causing corrosion to take place. If the unit is going to set for a while, best thing to do is drain the gas out. Take it out of the gas tank and carburetor, some people will buy a bottle of sea foam to refill the carburetor bowl. When it sets for long periods of time, then when they are ready they will drain the carburetor bowl and flush out with new fuel before starting. Another good tip is replace fuel filter, or if the unit you bought this year dose not have one buy one. The picture below shows the carburetor that in good working order, it has no green.