Yves Klein once described monochrome painting as an ‘open window to freedom,’ and across his artistic pursuits he sought to represent boundlessness. To this end, he developed the unique ultramarine pigment that he would patent, in 1960, as International Klein Blue. The hue was meant to evoke the perceptual space where the earth is indivisible from the sky. Just a few years later, James Turrell would begin experimenting with projection, testing the ways in which light produces immaterial architectures. Though working in different continents and contexts—Klein as a leading member of the Nouveau réalisme movement and Turrell in the Southern California Light and Space group—these near contemporaries expanded the possibilities of colour and light.