Goethe re-examines Newton's experiment by placing two white squares (quadrangles here in our drawing) by side of the blue and red ones. As he looks at them through a prism he sees that all four squares have identical edge color seams at top and bottom. In the white squares the edge colors are distinct and vivid. When the edge colors are formed of dark blue or red light, they are more or less discernible when they are intensified or extinguished by the color they are made of. In case of the blue square the red and yellow edge colors at top are barely noticeable on black background and it gives the impression that here the to of the blue square has dropped down. Blue and violet edge colors at bottom seem to continue the blue square downwards, so that the whole square seems to have moved down.

Red square on the other hand seems to stay in its place since the red and yellow edge colors just disappear in the red color of the square at top. At bottom blue and violet edge colors are extinguished as they are formed from red light.

Newton should actually have used violet color instead of dark blue for the first square in order to prove his point more vigorously, since violet color is refracted even more than blue color. Why did he use the dark blue color then? He used it because if he had used violet color the edge color seams would have been clearly visible. Newton must have experimented with both and seen that using violet color contradicts his theory but precisely with a deep blue color the edge colors are most difficult to see.