Francis Gerard was the eldest of four children, and raised at the family's thatched cottage in Barna, Co Galway, where his mother was a schoolteacher and his father was first stationed.
The family moved to the Cappagh Road, and some years later to Dublin, before returning to Galway again, where Colgan graduated from university as a civil engineer.
In June 1970, Gerry Colgan was co-opted to Galway Corporation to fill the vacancy created by the appointment of Bobby Molloy (Fianna Fáil) as Minister for Local Government.
One of his last acts as Mayor was to attend the opening of the Zapata Lexington semi-submersible oilrig, anchored south of the Porcupine Bank, one hundred and sixty miles west of Galway.
He married Carmell Small of Bohermore (in England in September 1944) and had children: Brian, David, Vivienne, Roy and Denise.