Art in the 1960s witnessed a revolutionary shift when Abstract Expressionism burst onto the scene from America.  In the previous decade, abstract art had been gaining ground in Britain.  Prominent among its exponents were artists such as Victor Pasmore who represented the 'constructionist' tradition, characterised by rigorous structures, a sense of order and a relatively small role for colour.  Some British artists were taking different directions. By the mid-1950s, Terry Frost, for example, while retaining linear structures in his painting, had become increasingly interested in the power of colour and the character of the paint surface. 

In 1956 the Tate Gallery was host to 'Modern Art in the United States', an exhibition which featured work by the founders of Abstract Expressionism, Willem de Kooning, Jackson Pollock, Mark Rothko, Robert Motherwell and others.  Three years later another exhibition, 'New American Painting' was shown at the Tate, as part of an eight-country European tour.  The energy, inventiveness, spontaneity and sheer size of these works had an immediate and dramatic effect, exerting an influence which continued throughout the 1960s and could be seen in the work of many British artists.  Patrick Heron was an early enthusiast for the new American phenomenon, though he was also a thoughtful commentator and critic, and his own work underwent change at this time.  Four Vermilions, for example, uses large areas of flat colour and a version of the hard-edge features found in some of the American art labelled 'Post-Painterly Abstraction'.  Red All Over by Terry Frost also deals in simplified forms using areas of colour in subtle relationship to each other. 

The Warwick collection contains some North American paintings from this period. Jack Bush and Gene Davis were leading exponents of 'Color-Field Abstraction', illustrated in Joseph's Coat and Untitled (1965), respectively, the latter showing a more formal aspect of the hard-edge style.  The English painter John Hoyland, like both Frost and Heron, visited New York in the early 1960s and met several of the leading American painters.  Hoyland's 6.3.66 uses large tracts of uninhabited colour, exploiting the optical effects of certain colour juxtapositions.  Among the new generation of British artists exhibiting in the 1960s were Tess Jaray, Jeremy Moon and Justin Knowles who also explored the interactions between colour and form, as seen in Salisbury Green, Cape Red and Blacks with Yellow and Green.