Sol LeWitt, A Wall Divided Vertically into Fifteen Equal Parts, Each with a Different Line Direction and Colour, and All Combinations, 1970
"LeWitt’s wall drawings are executed by assistants from the artist’s instructions. In this work, the lines are all equally spaced and drawn in coloured pencil. Each colour corresponds to a different type of line: yellow for horizontal, black for vertical, red for diagonal from left to right, and blue for diagonal from right to left. The lines are drawn in all possible combinations in fifteen rectangles, becoming denser from left to right. Through this layering, new colours and complex patterns emerge from LeWitt’s simple set of rules."