# Complementary color

RGB color wheel: The complementary colors yellow and blue face each other
Goethe's color circle for the symbolization of the human spirit and soul from 1809

Complementary color ( Latin complementum 'addition' ) is a term from color theory . In both additive and subtractive color mixing , those colors are considered complementary which, when mixed together, produce white or black. A pair of colors can be perceived as complementary, although (mathematically) according to the technical-physical values ​​(as with RGB , CMY ) it would not be exactly the opposite.

## Complementary color and color model

Which colors are complementary depends on the selected color model. The following complementary pairs are often mentioned:

With a color wheel as a model, the complementary colors are always opposite each other. So they are sometimes referred to as opposing colors . This term is fundamentally used in Hering's theory of opposite colors .

The complementary colors cancel each other out in the mixture, the newly created color is to be located at a point on the gray axis. For the CIELAB color model, the color {L, a, b} has the complementary color with the coordinates {L, -a, -b}, because the reflection axis is then the gray axis with a = b = 0. A corresponding calculation rule for an LCh color value results when the color angle h changes by 180˚ in each case.

## Complementary colors according to RGB / CMY

The following table illustrates the calculation rule for the basic colors of the RGB / CMY color mixture. For the values ​​R, G, B or Y, M, C, the corresponding complementary color is obtained by adding 100 percent, in 8  bits to the hexadecimal number "FF" and in 4 bits to "F". The reflection axis for complementary colors is neutral gray, with the decimal values ​​{0.5; 0.5; 0.5} or in 8 bits as `#808080`, correspondingly in 4 bits with `#888`. The example makes it clear: the web color `#3378F9` is `#CC8706`complementary or it `#99AA77`is too `#665588`. The number pairs must always add hexadecimally to the value "FFFFFF". The simplest calculation method is the XOR link with 0xFFFFFF.

colour Complementary color Playback in (monitor) RGB
R ot C yan # FF0000 # 00FFFF
G reen M agenta # 00FF00 # FF00FF
B lau Y ellow (= yellow) # 0000FF # FFFF00
Complementary example 1 # 3378F9 # CC8706
Complementary example 2 # FF8800 # 0077FF
Complementary example 3 # 8800FF # 77FF00
Complementary example 4 # 99AA77 # 665588
Complementary color colour complementary naming

## Effect and application

Complementary
• The complementary contrast is created on the one hand by the juxtaposition of complementary colors. On the other hand, it also establishes itself between any color and its afterimage , which is created in the eye when it is intensely viewed ( successive contrast ).
• Since complementary colors mutually exaggerate each other, complementary colors are also often used in advertising . Example: Meat on a green background or salad on a reddish background looks fresher.
• A complementary contrast can overstimulate the color receptors of the eye and the downstream nerve centers, which may be perceived as unpleasant. This happens when the colored areas collide hard, as in the illustrations below , where the colored area contrasts with the complementary colored text on it. In particular, flickering of the edges is recorded. The effect appears as an artistic stylistic device in hard edge painting, which emerged in the mid-20th century .
• The principle of complementary colors finds practical application in detergents . Blue substances are added, which suppresses the yellow tinge (yellowing) and the laundry appears whiter.
• Another practical application is the green clothing of surgical staff in hospitals: the green used corresponds exactly to the complementary color of red blood. Thus, the afterimage effect on the green surfaces is much less irritating for the OR staff than it would be on different colored clothing.
• If an object is irradiated by two light sources of complementary color at the same time, two overlapping complementary colored shadows appear behind it, if the light sources are at a certain distance from one another, and are surrounded by a background that appears white.

Red-blue glasses
3D glasses with red-green

Complementary colors are able to cancel or reinforce each other. With the anaglyph method , a spatial depth effect is achieved by offering different images to the left and right eyes. If the two partial images are printed in different colors and then viewed through color glasses in complementary colors , the intended spatial impression is created. Each eye is fed the respective image separately through different color filters. Usually printed in the complementary pair red-green, the green partial image is allowed to pass through the green glasses filter as white, i.e. in the color of the paper, and is not perceived there. However, the red partial image is blocked by the green glasses filter and perceived as black because of the contrast it creates with the paper. Since the red filter conveys the other partial image to the other eye according to the same control, both anaglyphic partial images are seen separately again and give the spatial impression. Depending on the usable pair of printing inks and glasses, other complementary pairs are sometimes used, in the patented deep vision system cyan with red and ColorCode 3D process glasses with blue in front of the right eye and yellow in front of the left.