Artist. Born in Kilmarnock and educated at the Academy in that town, where his artistic talents were already well-developed. Colquhoun won a scholarship to train at the Glasgow School of Art, where he met Robert McBride (1913-66), who became a life-long companion. When Colquhoun obtained a bursary to allow him to travel to Italy, the pair went on to study in Europe (1938-9). Colquhoun served as an ambulance driver in the Royal Army Medical Corps during World War II, but having been injured he returned to Britain (1941) where he took a studio with McBride at Bedford Gardens in London.
Colquhoun's early work was greatly influenced by the colours and light of the Ayrshire countryside and includes pictures of agricultural labourers and workmen portrayed with a genuine sense of feeling. This developed into a brooding, expressionistic style, which was strongly influenced by Picasso. Austere, yet precise, he portrayed tortured and agonised figures in oil, using characteristic browns and reds. His interest in human and animal forms is exemplified by Woman with Birdcage, displayed in the Bradford Art Gallery, Woman in Green, on show in the Aberdeen Art Gallery, and Two Scotswomen, held by the Museum of Modern Art (New York).
Colquhoun also illustrated books and, together with MacBryde, designed several theatre sets, including Gielgud's Macbeth, George Devine's King Lear at Stratford and for the Scottish Ballet Donald of the Burthens produced at Covent Garden for Sadler's Wells (1951).
The 'Two Roberts' were evicted from their studio in 1947 and Colquhoun died in London in relative obscurity.