• I had left the visible, physical blue at the door, outside, in the street. The real blue was inside, the blue of the profundity of space, the blue of my kingdom, of our kingdom!.. ..the immaterialisation of blue, the coloured space that can not be seen but which we impregnate ourselves with.

    "Yves Klein, 1928 - 1962, Selected Writings". Book by Yves Klein (p. 41),