A color never appears alone. What surrounds it changes how it looks. This is called simultaneous contrast. The French chemist Michel Eugène Chevreul, who ran the dye works of the Gobelins tapestry factory in Paris, studied it closely and published his findings in 1839. Some dyes, such as a black wool, were said to look weak. He found that the dyes were fine: the threads next to them were changing how they looked.
Key idea
A color looks lighter on a dark ground and darker on a light ground. On a colored ground, it takes on a hint of that ground's complement.
Why it works
The eye and brain exaggerate differences at edges. Nerve cells that respond to one area are damped by the activity of their neighbors (scientists call this lateral inhibition). Next to black, a gray seems lighter; next to red, a gray is pushed away from red, toward a greenish gray.
Worked example: Which gray looks lighter?
Two identical middle-gray squares sit on two grounds: one black, one white. Which looks lighter?
- The surrounding value pushes the square the other way.
- Black around it makes it look lighter.
- White around it makes it look darker.
Answer: The one on black.
Common mistake
Judging a color alone, on a white palette, and being surprised when it looks different in the picture. Test a mixture next to the colors that will surround it. Painters often dab a test stroke right on the canvas.
The painter and teacher Josef Albers built a whole course on these effects in his book Interaction of Color (1963), with exercises that make one color look like two, and two colors look like one.