As a reply to Newton's theories, Goethe developed a Theory of Colour (Zur Farbenlehre, published in 1810), which became a personal obsession in his last years, and which he considered more important than his literary works, but which was not well received by contemporary scientists. Goethe wanted to create something more basic than a mere theory of optical science — he intended his colour theory to be a paradigmatic model for natural science in general, and was concerned with the psychological effects of each colour, as well.

For instance, where Newton defines darkness as the absence of light, Goethe presents darkness as polar to, and interacting with, light. In Goethe's view, the basic polarity is not the contrast between black and white, as he doesn't consider black and white to be colours, but the opposition between blue and yellow. His approach was more empirical and experimental than Newton's, and even though all his experiments have been proven to be correct, this work remains more popular with philosophers than with physicists, mainly due to its weak theoretical part.

Goethe developed this colour wheel concerning the "Allegoric, symbolic, mystic Usage of Colour". In his handwritten notes, he assigns a human character trait to each colour. The right side with the warm colours is denoted positive, the left one with the cold colours is denoted negative. By adding red shades, one arrives — on the positive side via orange, and on the negative side via violet at the cumulation of pure red (crimson). The German terms in the wheel translate to:

"Rose of temperaments": Together with Friedrich Schiller, Goethe developed the "Temperamentenrose" with regard to the sensual-moral effect of colours. The same way complementary colours are opposed in the colour wheel, the four humors are opposed in pairs. The sanguine and the melancholic form the humors of feeling, the choleric and the phlegmatic are the humors of activity. Each humor is assigned to three types of human character. In the sense of progression on the active (red) side, there are adventurers, heroes, and tyrants, while on the passive (blue) side, there are teachers, philosophers, and pedants (the latter are considered collectors striving to complete knowledge). Purple as the combination of the intensified poles of the colour wheel represents the ruler, who is opposed by the poet as his harmonic complement. The German terms in the wheel translate to: