BOTH GRAY RECTANGLES ARE THE SAME! This is a beautiful example of how to create brightness using colors of opposite values to generate contrast. Rembrandt was the master of this technique.*
* Rembrandt used his renowned technique called "Chiaroscuro" Italian, from chiaro clear, light + oscuro obscure, dark. When you see Rembrandt's paintings you can distinguish two clearly defined tonal values: Light and dark. Because the dark colors are rich and deep, the light areas of the painting appear to shine almost with phosphorescent quality. Did he use a special, brighter white than anyone else? Of course not. The master of the chiaroscuro used color interaction, thus making his colors appear lighter or darker than they would be individually.