Wold herring was an expert in color perception. He paid less attention to the physics of wavelengths than to the subjective experience. Psychologists regard his concept of red, yellow, green and blue fundamental colors as primary in human visual pairings theories were the basis for the color system of Frederick Oswald, German physical chemist and natural philosopher. The key points of Oswald system were the form of the squat double cone and the systematic presentation of all hues in their variations.