But what is this line? and why is it green?

The Green Line is a reference to the Metro North's Hudson line that goes along the glorious Hudson from NYC to Croton Harmon, stopping of course at Shangri-La, also known as Dobbs Ferry. Being on one of the others lines is basically worse then not being on one at all, but still not as bad as taking the long Island Rail Road.

If you don't know...now you know