The document discusses different types of color saturation on a color wheel. The outermost colors are the most saturated prismatic colors, while the inner colors are the least saturated achromatic grays. It notes that gradients between colors contain an infinite number of hues. When setting up saturation gradients using color wheel complements, the achromatic grays are not directly on top of each other. The document advises paying attention to value differences between saturation steps when creating color studies.