As the two previous mentioned, leaf peepers pack the campgrounds in September and October. Reservations are highly recommended if you want to be sure of finding a place at night, you need to make those reservations now as most places are gone by May 1st.
September color appears in NY on north. October color occurs in the Blue Ridge from mid-October to Oct 31.
To plan, pull out a map and pick towns near mountains. Go to
http://www.woodalls.com/ and insert the town names to pull up a list of campgrounds in the area. Schedule by calling the cg phone number listed.