Colors that are in some way opposite to one another are referred to as complementary colors. Such colors make up the complementary color wheel. Avery defined Complementary Colors as early as 1895. In color science, two colors that combine to produce gray are known as complementary colors. In most color models, complementary colors lie roughly opposite to each other, with white towards the center. Colors that are placed opposite to each other on the Blue, Yellow, Red color wheel are complementary color wheels and when mixed, they produce the color gray.

In complementary color wheels, in most cases, fully saturated hues are considered. However, brightness and saturation are characteristics of colors. Brightness is basically the amount of the color wavelength. Thus, in a formal complementary color wheel, any color made of a particular wavelength can be balanced to produce white or gray by adding a particular brightness of the complementary wavelength.

Complementary color wheel comprises of:

Red and cyan, a mixture of blue and green Green and magenta, a mixture of red and blue Blue and Yellow, yellow being the mixture of green and red However, traditionally, complementary colors consist of the following pairs:

Green and Red Orange and Blue Purple and Yellow Primary colors are red, blue and yellow. Usually, the compliment of a primary color is made by combining the other two. Additive and Subtractive Color Mixings Light mixtures are called additive color mixing. As for example, the addition of red and yellow gives green. The behavior of dye or paint or pigment or ink mixings is referred to as subtractive color mixings. For instance, the combination of the complmentary colors, yellow and cyan, give green. Color contrasts can be used to accentuate information or highlight items The complementary color wheel finds its use in the preparation of aesthetic arts and graphics. Complementary colors placed adjacently make each other come out and look vivid. This property is very useful when mixing colors. The human eye fails to focus on both red and blue simultaneously. This creates eye fatigue. As for example, using red type on a blue background will repel the readers and the message will not be registered by the target audience. Complementary colors should be chosen keeping this aspect of colors in mind. It is a wiser option to go with colors that belong to the same color family – warm colors or cool colors. The two groups should not be mixed in type font.

In artistic complementary color wheels, the complementary colors may not follow the precise scientific definition of complementary colors. While mixing the color of paints, Newton's color wheel is taken as the reference for complementary colors. According to this, complementary colors are those that cancel each other out to give any achromatic hue. An achromatic color is Gray, White or Black. In this complementary color wheel the fiery hues, which are the most saturated ones, are placed on the outer margin. The achromatic white is again at the center.

A very handy tool which automates the search for matching colors with Hex and RGB codes can be found at Design Color Wheel.