That depends on whether you established residence/domicile in your college town.
You can only have one residence/domicile at any given time. Whichever residence/domicile you had before moving outside of the United States is your "voting residence address" as an overseas voter.
Living in a location while you are temporarily going to school doesn't necessarily make that your residence/domicile for voting purposes, even if you lived there for several years. Your voting residence is determined by the last place where you maintained residence that you considered your home and intended to stay. Depending on your individual circumstances, your voting residence address may be your parents' residence address or your college address.
If as a student you registered to vote in the college town, got a driver's license from that state, rented an apartment, and basically conducted your life as a resident would, then you established residence/domicile in the college town, even if you didn't know whether you would remain there after graduation.
See the two examples below to get a better idea of if your college town is your last legal voting residence.
Mary graduates from high school in Texas and then attends Northwestern University in Evanston, Illinois, for four years. While she is a university student, she registers and votes in Illinois. Upon graduation, she joins the Peace Corps. She goes to Washington, D.C. for one month for training, medical examination, etc. and then is assigned to Malawi, a country in Africa. When she completes her Voter Registration/Absentee Ballot Request form in order to vote from overseas, her last U.S. residence address is where she last lived in Evanston, Illinois, and she will receive an Illinois absentee ballot. Note that she will not vote in Washington, D.C. because she was only there temporarily and never resided there.
Joe graduates from high school in Buffalo, New York, and then he attends Columbia University in New York City for four years. While he is a university student, he votes by absentee ballot, using his parents' address in Buffalo as his voting residence address. Upon graduation, he moves to France. When he completes his Voter Registration/Absentee Ballot Request form in order to vote from overseas, his last U.S. residence address is the address where he had resided in Buffalo. Even if his parents move away from that address, or pass away while he is living overseas, he should use that address as his voting residence address for as long as he lives overseas or until he moves back to the U.S.