A phenomenon where a solution or material’s hue depends on the traversed medium's thickness or depth as well as the absorbing substance's concentration. It can be seen in an absorption spectrum containing a single, narrow, yet deep local minimum and a single, wide, yet shallow local minimum. An example includes a pumpkin seed oil's layer that measures less than 0.7mm in thickness so that the oil seems bright green, but if the layer is thicker, appears bright red.