A native of Millstreet, County Cork, Billy Coleman still resides there and works as a farmer outside of Kanturk. His interest in cars developed early, with Coleman recalling his father allowing him to steer a car from his knee at age five. His father, Paddy Coleman, was the local Ford main dealer and owned a motor garage in Millstreet, where Coleman spent time, further nurturing his interest in cars. Although he studied commerce at University College Cork, Coleman preferred farming and undertook it full-time after concluding his racing career.
Coleman's first racing car was a Ford Cortina, which he drove in 1967. In 1969, he acquired a crashed Ford Escort, which he repaired and converted into a rally car. Driving this self-prepared green Ford Escort Mark I (registered TIU 250) in 1969, Coleman won a special stage ahead of Roger Clark's works Ford Escort.
Coleman dominated rallies in Ireland and Britain throughout the 1970s and 1980s. He also competed in the international arena, including events in Corsica and Monte Carlo. During his racing career, Coleman drove a variety of cars, including the Ford Cortina, Ford Escort, Alpine-Renault, Lancia Stratos, Fiat-Abarth 131, Opel Manta 400, Porsche 911, Porsche 959, MG Metro 6R4, and BMW M3.
Between his active racing years of 1968 and 1987, Billy Coleman started in 128 national and international rally events and claimed 29 victories.
Coleman's two sons, Robby Coleman and Gordon Coleman, also participate in Irish and British racing events.
In 2006, Coleman was awarded the RTÉ Sports Hall of Fame Award for his achievements in rallying. He is also featured in the "Tarmac Titans" DVD series on rally legends.
The Billy Coleman Young Driver of the Year Award was conceived in 2000 through a partnership between Motorsport Ireland, Sport Ireland, and Team Ireland. The award's aim is to "motivate young Irish rally drivers to step up into the international arena and rival the achievements of the young Billy Coleman."
Irish-American billionaire and philanthropist John Campion attributed much of his motivation to succeed to Billy Coleman's achievements as a rally driver. Campion supported the launch of the Team Ireland Foundation in Dublin in 2016. In his speech, Campion stated: "As a young boy in Cork I found myself struggling with school and at a loss as to what I would do with my life. But I always felt a bond with motorsport after witnessing Billy Coleman, a farmer who became a world rallying icon, competing near my home in Cork. After seeing Billy rallying I realised then that if you put your mind to it, you could achieve anything." John Campion emigrated to the United States, where he became the chairman and CEO of an international energy corporation, and a philanthropist focusing on health, education, and nutrition, as well as a sponsor of racing drivers through his motorsports organization CJJ Motorsports. Campion's collection of Lancia rally cars was inspired by the Lancia Stratos HF driven by Billy Coleman in 1978.