Complementary Colors are any two Hues positioned exactly opposite each other on the Basic Color Wheel. To be sure, knowing where they lie on a Color Wheel is basic. But even more important, is understanding what this means in a practical sense.
Keep reading to learn how these pairs of colors can help you create more interesting mixtures for your projects.
As you can see directly above, the most commonly used pairs of Complementary Colors are:
YELLOW / PURPLE
RED / GREEN
BLUE / ORANGE
Take another look at each mixture, both from left to right and right to left. You can see that when you gradually add a speck of each color's Complement, the resulting mixture becomes less and less intense. Eventually the color is totally neutral.
This is the perfect way to easily knock down the intensity of any color if it's too vibrant. Sometime beginning artists try to reduce the intensity of a vibrant color by adding black. This works too, but it also creates a Shade and the underlying vibrancy of the original color is often lost.
But you must be careful when mixing in a color's Complement. The color changes super quickly so be sure to add extremely small specks at a time.
So why do Complementary Colors react to each other the way they do?
If you look closely at the Color Wheel at the top of this page, you'll notice a few things.
Although it's true, when Complementary Colors are blended together, they neutralize each other, they interact differently when placed side by side. As mentioned in the last paragraph, they are the two colors with the highest contrast. As a result they actually intensify each other when sitting next to each other. In Color Theory this phenomenon is called Simultaneous Contrast.
Photographers and artists often take advantage of this fact to create intense drama. Maybe that's one of the reasons we are always so attracted to sunsets. The contrast of Orange and Blue vibrate to capture our attention.
In the same way, if you want to paint the sunset above, you will literally achieve a wonderful result by using only two colors, Blue and Orange plus White and Black to make Gray.
In another example, the painting at left is by Georgia O'Keeffe.
Just observing the main focus of her painting at this time, you can see she has used the Complementary Colors Red and Green to paint her subject.
Notice how she blends the Red into the Green on the leaves to darken them. And she's also added a speck of Green into her Red to reduce the intensity.
Mixing tiny specks of each color into the other creates automatic harmony. Otherwise each color would fight for your attention and jump off the canvas.