When you take a look at the picture are some of the red lines darker than others? Showcase the Bezhold effect with any of these optical illusion gifts. Explanation caption says the following: "Notice that the red seems lighter when combined with white & that the red appears darker when combined with black. This optical illusion is named after Wilhelm von Bezhold (1837 - 1907), who discovered that a colour may appear different depending upon its relation to adjacent colours." Educational visual fun psyche / psychology attitude for those who understand that colour is relative!