This is an interesting phenomenon. Most people don't realize how color interacts with other colors. This swatch contains only 3 colors - blue, yellow, and gray. When the gray dots are placed on the blue background, they join with the color and rest comfortably in a value that is slightly lighter than the dots. But when the same color dots are placed on top of the yellow background, they vibrate and appear to turn almost lavender. The dots did not absorb the background color, since the background was completely dry when I placed the dots on it. Artists must pay attention to the colors they are using in comparison to the surrounding colors if they are attempting to make a particular statement.