(Chapter 4 from Interaction of Colors book)
The author, Josef Albers, described an experiment to discover the powerful fact that color is relative. Specifically, color is relatively to other colors around it. This simple fact is easier to observe with examples than to explain the technical rationale.
The image below randomly selects 3 colors. One color is applied to the panel on the left, another color is applied to the panel on the right. The 3rd color is applied to the small boxes in the middle of both panels. After looking at several examples, hopefully, you will observe that quite often the small boxes seem to be different colors!