I don’t paint light. I present a colour situation which releases light as you look at it

Riley’s introduction of colour was undertaken with some trepidation. Previously, Riley’s use of black and white depended on the disruption of stable elements. For a long time she was aware that no stable basis could be found for colour. The perception of colour is entirely relative: every colour affects, and is affected by, its neighbouring colours. Riley gradually came to accept this principle of instability, making it the basis of her subsequent engagement with colour.

Late Morning 1967 developed the theme of a progression of vertical stripes in contrasting colours, a formal device that she would employ until the mid-1970s. Her adoption of the colour stripe was, however, not simply a stylistic choice. Rather it was a practical expedient intended to maximise the interaction of adjacent colours. Nor did Riley employ colour as an end in itself. As these paintings show, the effect of this interaction is to create an impression of coloured light: one of the most compelling features of Riley’s art. The eye is seduced, as it were, transported into a kind of relaxed gaze which more readily receives the slow, steady, chromatic diffusion. Though abstract, paintings that are so intimately connected with the experience of light evoke a sense of recognition. As Riley commented: ‘colour inevitably leads you to the world outside.’

The desire to explore the behaviour and intensity of the light liberated by this colour interaction led Riley to use, in turn, the principal directions of the stripe format. These include the horizontal stripes in Rise 1 1968 and Apprehend 1970 and diagonal stripes in Veld 1971 and Rattle 1973. In Orient 4 1970, Riley destabilised the vertical stripes further by crossing-over and tilting these elements. In Zing 1971 this cross-over device was extended so that the stripes appear to twist repeatedly around each other. Riley’s engagement with colour stripes reaches its apogee with two major paintings: Cantus Firmus 1973 which reintroduces black and grey, and Paean 1973, an early indication of Riley’s later involvement with the evocation of space