Douglas Hamilton Colquhoun was born in North Shields, Northumberland, England on 6 August 1882. He was the son of a Scottish father, Duncan Colquhoun, and a Liverpool-born mother, Martha Maddocks; he had two elder brothers, Duncan and Archibald. 

Colquhoun spent his early years living in Aberdeen, Scotland, appearing there on the 1891 census; the family later returned to England, settling in Liverpool where they appeared on the 1901 census as residents of Willoughby Road, Waterloo. He later married but is believed to have divorced at some point. 

In April 1912 Colquhoun was serving as 7th engineer aboard the eastward-bound voyage of the Carpathia when that ship rescued the survivors of the Titanic. 

Douglas Colquhoun remained a resident of Liverpool for the rest of his life and served in the merchant fleet throughout WWI and again in WWII. He was chief engineer officer aboard the cargo ship Dafila when that vessel was torpedoed on 18 March 1943 and he was among the lost, being killed in the explosion.