Oswald Bernard Colnaghi, a London art dealer, was the son of Martin Lewis Gaetano. His older brother Martin Enrico Luigi Gaetano (Henry) Colnaghi, was also an art dealer.
The Colnaghi's art dealing business had its origins in a firm founded in the mid-seventeenth century in Paris and London by Giovanni Battista Torre (d 1780), a pyrotechnist and printseller who dealt in English etchings and mezzotints. In 1785 Henry Colnaghi's grandfather Paul Colnaghi became Torre's partner in London. In 1788 he completely took over the London side of the business, and began publishing reproductive engravings of portraits, and historical and topographical subjects, receiving a Royal Warrant from George IV to supplement the royal print and drawing collection.
Successive generations of the Colnaghi family built up the range and reputation of the business, and in the 1830s, under the management of Henry's uncle Dominic Colnaghi, the firm's premises at 14 Pall Mall East, London, became a hub for important artistic, literary and political figures.
A significant number of Whistler paintings passed through the hands of the firm of Colnaghi, including La Mère Gérard (2) (YMSM 27), Harmony in Green and Rose: The Music Room (YMSM 34), The Coast of Brittany (YMSM 37), Whistler in his Studio (YMSM 63), Study in Grey for the Portrait of F. R. Leyland (YMSM 95), Arrangement in Black: Reading (YMSM 224), An Orange Note: Sweet Shop (YMSM 264), Note in Blue and Opal: The Sun Cloud (YMSM 271), A Courtyard with an Open Workshop and a Standing Woman (YMSM 308), Coast Scene: Bathers (YMSM 326), Study for 'Brown and Gold: Lillie "In our Alley!" ' (YMSM 463), Violet and Rose: Carmen qui rit (YMSM 506), The Sea, Pourville (YMSM 520), The Shore, Pourville (YMSM 521) and Howth Head, near Dublin (YMSM 538). The company also bought and sold over one hundred watercolours, pastels and drawings.
In 1901 O. B. Colnaghi was living on own means in Chiswick.
The Post Office Directory of Stationers, London, 1872; UK census 1901; Colnaghi's, 1760–1960, London, 1960; Young, Andrew McLaren, Margaret F. MacDonald, Robin Spencer and Hamish Miles, The Paintings of James McNeill Whistler, New Haven and London, 1980; MacDonald, Margaret F., James McNeill Whistler. Drawings, Pastels and Watercolours. A Catalogue Raisonné, New Haven and London, 1995; 'Colnaghi's', The Grove Dictionary of Art Online, ed. L. Macy, http://www.groveart.com (accessed 6 September 2002).