Colin Buchanan was born on August 22, 1907, in Simla, India. He was the son of William Ernest and Laura Kate Buchanan. Buchanan was born into a family of civil engineers whose work helped to shape cities. His great-grandfather practiced civil engineering in Edinburgh, Scotland. His grandfather traveled and worked as an engineer all over the world; his uncle Sir George Buchanan was knighted for building a harbor in the city of Rangoon, India, and his father, also an engineer, built several major structures, including a water supply system in Simla. India, which is where Buchanan was born. For the first three years of his life, Buchanan remained in India; then his mother brought him and his sister back to England, where he remained for the remaining years of his youth.