Executed in 1985, Bright Shade illuminates Riley's ground-breaking investigations into the optical potential of colour. Hypnotically evading perspectival resolution, the uncompromising rectangular canvas is articulated by alternating vertical stripes of vivid orange, pink, green, red, blue and yellow, which, when viewed from afar, create a dazzling chromatic experience that extends beyond the picture plane. Such dramatic visual effects have anointed Riley as the undisputed leader of the Op art movement. Nevertheless, her preoccupation with the mechanical contingencies of colour, and the sensory and perceptive effects that can be produced through constructing a rational architecture of form in which colour resides, extends Riley’s impact and influence on contemporary painting far beyond the confines of a single movement. Maintaining an unparalleled relationship to the formal, ‘plastic’ concerns of painting inherited from the likes of Georges Seurat, Paul Signac, Paul Klee and Piet Mondrian, the British artist has developed a pictorial language that is remarkably unique. With Bright Shade, Riley has produced a visually compelling, technically adroit, and theoretically enlightened masterwork of pure chromatic sensation.

In the winter of 1979-80, Riley travelled to Egypt where she visited the Nile Valley and the Pharaoh tombs in the Valley of the Kings. Inspired by the art which adorned ancient burial sites, Riley was especially drawn to the symbolic use of six hues – red, blue, yellow, green, black and white – which represented aspects of Egyptian life. The present painting is from the body of work made in the years following her travels, where Riley harnessed a range of intense hues – her own 'Egyptian palette' – within a formal linear arrangement. With Bright Shade, Riley engenders a dialogue between the formal structure of the stripes and notions of weight, density, brilliance and opacity. Constructive rather than descriptive, Riley's use of colour exploits its inherent instability, allowing her the freedom to create the visual interactions which would go on to dominate her work for the next decade.

It is between the dialectical fray of composition and perception that Riley situates her work. As a student, Riley made studies from the works of Georges Seurat, who was influenced by the empiricism of Charles Henry and his theory that mathematical formulation could directly explain aesthetic results. Rejecting Seurat’s meticulous pointillist technique, she instead concentrated on the artist's systematic distillation of colour and his balanced use of complementary hues to delineate light, shade, depth and form. Bright Shade includes echoes of this early exploration of colour, whilst also incorporating the vigorous structural emphasis of her early black and white geometric paintings. Inspired by the ‘all-over’ canvases of Abstract Expressionists like Jackson Pollock, Riley refined their multi-focal vernacular into her own unique artistic language. This is gracefully embodied in the pulsating stripes of the present work, as Riley combines the rigid logic of early colour theory with a complete painterly engagement with the surface of the canvas, resulting in a visual sensation that oscillates between the ‘plastic’ neutrality of the stripe and the optical brilliance of her colour palette.