Georg Schmidt writes about the group of watercolours to which Rot Stufung belongs: "A series of watercolours Farbstufungen (colour gradations) originate from 1921-23 of which the Kristall-Stufung is one. Klee worked on these pictures with a lasierenden Verfahren (varnished method), whereby translucent colours (watercolours) are applied in a layered fashion. Klee describes this whole method as farbig belastete Helldunkelmalerei (chiaroscuro painting laden with colour). Leaving the black or the white, the intermediate stages gradually become farbig belastet (laden with colour). The contrast of black and white brings about a strong three-dimensional gradation. The growing and diminishing forms push each other around, and fade into each other. Through this kind of movement of the colours, and the dynamic relationship of the colour values to each other, Paul Klee allied himself to Robert Delaunay, whose colour studies he had systematically examined in conjunction with Goethe's teachings on colour, and that of Rung. He is certainly less interested in visual experiments and discoveries, as for instance in the Futurists or Marcel Duchamp; rather he orientated himself towards musical parallels. The layers of colour are reminiscent of musical scales...Will Grohmann has described the Farbstufungen as Fugenbilder (paintings of fugues), which is only partly correct. Whereas a fugue by Bach preserves its identity, Klee's paintings develop from a primary state to a final form, eg. from a circle to a rectangle. In fact the Farbstufungen display a surprising similarity to the Reflektorischen Lichtspielen (reflected plays of light), which were first executed in the summer of 1922 by Ludwig Hirschfeld-Mach and Kurt Schwedtfeger at the Bauhaus." ("Auszug aus der Rede zur Gedächtnisfeier", in Paul Klee, 50 Werke aus 50 Jahren (1890-1940), Hamburg, 1990, p. 84)