This link provides a rough account of Goethe's theory of colour, but it follows the modern tradition of treating it as a mistaken physical theory of colour which is best understood as theory of colour perception:
The Dark Spectrum I: Goethe and the imaginative interrogation of color https://www.refractionsblog.com/single-post/2018/11/19/The-Dark-Spectrum-Goethe-and-the-imaginative-interrogation-of-color It would be interesting to place thermometers in Goethe`s dark spectra much like Hesrchel did over 200 years ago in Newton`s white spectra when he discovered infrared radiation. Here is a modern demonstration of Herschel`s experiment: Demonstration of Existence of Infrared Radiation (Herschel Experiment) https://www.youtube.com/watch?v=2LkQVlQRpfE Harry
