The point of view of Runge, his approach to colors had not the wideness of Goethe's universal genie. He wrote on colors from the position of a painter, who was primarily interested in the difference between transparency and non-transparency. This is a very practical view considering that the traditional oil painting technique is currently using white or black to modify the intensity of every color tone. But both white or black cannot be transparent media. Runge's idea was to place the pure colors (a palette of 12 colors Fig.3) at the equator of a three-dimensional ball, that would have white as a North pole (fig.4) and black as a South pole (fig.5). The 12 color tones would be mixed step by step ether with white or with black, depending of their position towards the north or towards the south. A kind of color catalog appears in this way. The very center of the ball or "sphere" appears if I would cut it in the middle from North to South. It is a middle Grey. The same grey as if I cut at the equator and imagine the center being a perfect mixture of the 12 tones.
Runges Color Sphere could have been helpful for painters of his century, but the development of the color industry since the beginning of the 20th century minimized the importance of his work. Runge also brings no special help for an understanding of the light. But as we will consider in further lessons his question concerning the transparency becomes real in the practice.