Diver came to Reed from the University of Pennsylvania, where he served as the Charles A. Heimbold Jr. Professor of Law and Economics and, before that, as dean of the law school. He holds a law degree from Harvard and served as a faculty member at Boston University School of Law and as a visiting professor at Harvard's Kennedy School of Government. He held posts with the Commonwealth of Massachusetts and with the Mayor's office in Boston and has been a member of the executive committee of the Harvard Law School Visiting Committee, a trustee of the Lawyers' Committee for Civil Rights Under Law, and a trustee of Amherst College, where he received the honorary degree Doctor of Laws in 1990. Diver was the fourth Amherst College alumnus to head Reed. Other Amherst alumni who have been president of Reed are Dexter Keezer, Duncan Ballantine, and Paul Bragdon. In 2004, the University of Pennsylvania School of Law honored Diver with the creation of the Colin S. Diver Distinguished Professorship