Problem
First describe your experience. What were the objects you used? How did you change the lighting? What did you notice? Now compare this experience to something else. Something you thought was white is no longer white in comparison to something else. Two things you thought were the same are actually quite different when closely examined. Changing the lighting (or perspective) can completely change how you see something. The experiment targets a very concrete situation, but can you relate this to something less physical - maybe a social situation or scenario? Your example should not center on another basic color comparison.