Complementary pairs a color with the one straight across the painter's wheel, 180° away: red with green, yellow with violet, blue with orange. It is the strongest contrast of hue a harmony can give. A notan has three colors, so the third is a lighter version of the first.
What it does
Press “Comp” under “Harmonies”. Its diagram is two dots joined straight through the center of the wheel.
With a color locked, that color stays exactly as it is. The next card in the order Front, Back, Ground takes its opposite, at the same saturation and lightness. The card after that takes the locked color's own hue, 25 points lighter on a lightness scale of 0 to 100 (HSL lightness, which none of the sliders shows directly).
- Front locked: the Back is its opposite; the Ground is a lighter front.
- Back locked: the Ground is its opposite; the Front is a lighter back.
- Ground locked: the Front is its opposite; the Back is a lighter ground.
The lightness step stops at white, so a locked color that is already very pale gets a lighter partner that is simply white.
With nothing locked, Comp invents a palette. The selected card gets a random hue, the next card in the order gets the opposite hue, and the card after that gets the selected card's hue again. Saturation and brightness are drawn at random for each, with the ground kept pale. With the Front selected, that means a back in the front's complement and a pale ground in the front's own hue.
Once armed, the pair turns together. Drag the front's hue from blue toward violet and the back swings from orange toward yellow, staying opposite all the way.
Why it works this way
In a paper notan the front and back meet along every fold: each flipped piece is joined to the sheet at the edge it turned over. With the Front locked, Comp puts the opposites on exactly those two sides, so every fold becomes a meeting of opposites. It is the loudest thing a harmony can do to a notan.
Two opposites alone would leave the third color with nothing to be, and a third, unrelated hue would crowd the pair. So the third is a lighter version of the locked color: a quiet partner that shares its hue with one of the pair and gives the design a step of lightness. A notan needs that step more than it needs a third hue.
There is a caution built into the choice. Two strong complements at the same lightness can seem to shimmer where they touch, as if the eye cannot settle which is in front. That can be exciting, or tiring. The lighter third, and the brightness sliders, are there to calm it.
The metaphor
A complement, from the Latin complementum, is something that fills up or completes. The idea is that two colors together make a whole, and each medium has its own version of that whole. Shine a color of light together with its complement and you get white: the pair completes the spectrum. Mix a paint with its complement and you get a dark, muddy neutral: the pair cancels to gray or brown. Stare at a red patch for half a minute, then look at a white wall, and a pale blue-green ghost appears: the eye completes the red on its own.
That is where the metaphor breaks, and it breaks usefully. There is not one opposite for each color but at least three: the painter's (red and green), light's (red and cyan), and the eye's afterimage, which falls close to light's answer. A color wheel is a claim about which of these you mean. Studio Notan means the painter's, because that is what a color lesson teaches. The other two are no less true; they answer different questions.
A history
In art
Goethe, in his Theory of Colours of 1810, put the afterimage at the heart of his theory: the eye, shown one color, produces its opposite to make itself whole, and the colors opposite each other on his circle are the ones that call each other up. Chevreul turned the observation into a working rule. Investigating complaints about the dyes at the Gobelins tapestry works, he found that much of the trouble lay in the eye rather than in the chemistry: colors placed side by side push each other toward their own opposites. His law of simultaneous contrast, published in 1839, gave painters a reason to set complements side by side on purpose, since each makes the other look stronger.
Painters took it up. Vincent van Gogh, writing to his brother Theo in September 1888 about The Night Café, said he had tried to express the terrible passions of humanity with red and green: a blood-red room around a green billiard table. The complementary pair was not decoration there; it was the subject.
In printing
Printers meet complements every day, mostly as something to manage. In four-color process printing, a color built from cyan, magenta and yellow often carries a hidden gray: the part where all three inks overlap, which is where a color meets its complement and cancels. The techniques called under-color removal and gray-component replacement take that gray out and print it with black ink instead. That uses less ink, dries faster, and holds neutrals steadier on press.
Complements also gave print its first 3D. In 1853 Wilhelm Rollmann described looking at a drawing made in two colors through glasses of two colors, so that each eye saw only one of the drawings. In the 1890s Louis Ducos du Hauron printed photographs the same way, two negatives printed one in red and one in blue or green on a single sheet. Modern red-and-cyan glasses work because the two filters are complements in light: what one lets through, the other blocks.
In technology
In the 1870s the physiologist Ewald Hering proposed that color vision is organized in opposing pairs: red against green, yellow against blue, black against white. His argument was that you can see a reddish yellow but never a reddish green. The idea became a backbone of modern color science. The CIELAB color space, standardized in 1976 and used in color management and print today, has one axis running from green to red and another from blue to yellow: Hering's pairs turned into coordinates.
Screens took another path. In the HSV model of 1978, a complement is simply the hue plus 180°, which pairs red with cyan and blue with yellow: right for light, wrong for a paint box. Studio Notan's “Comp” keeps the painter's answer by turning hues on a red-yellow-blue wheel instead, so a student's blue still meets its orange.
In professional software
Every harmony tool has a complementary rule. Most professional programs also have a second kind of opposite: a command that turns a color around the wheel of light. Knowing which one you are using is the skill that transfers.
- Adobe Color. Choose ‘Complementary’ and the five colors of the theme are drawn from the base color and its opposite on a red-yellow-blue wheel, so blue still meets orange.
- Adobe Illustrator. The ‘Color Guide’ has ‘Complementary’ and a variant, ‘Complementary 2’. Separately, the ‘Color’ panel’s menu has a ‘Complement’ command that works on screen color: it turns a pure red into cyan and keeps its lightness.
- Adobe Photoshop. ‘Image › Adjustments › Invert’ (⌘I, or Ctrl+I on Windows) sends every color to its opposite on the wheel of light and swaps light for dark as well. It makes a negative, not a harmony.
- Procreate. ‘Complementary’ is the first of the five modes in the ‘Harmony’ tab: one reticle on your color and one straight across the wheel.
What carries over. In brand and interface work a complement is rationed. One color carries the page, and its complement marks the few things that must be seen: a button, a price, a warning. The pitfall is the shimmer this chapter describes. Two complements at the same lightness are hardest on small type, so never set text in one over the other without a clear step of light and dark between them, and check the pair with a contrast checker such as the one in Adobe Color.
Try this
- Lock the Front, give it a strong blue, and press “Comp”. The back turns orange and the ground a lighter blue. Cut a shape and flip it: every fold is blue against orange.
- With the harmony still armed, drag the front's marker slowly around the wheel and watch the back stay opposite.
- Lower the brightness of the back until the fold stops shimmering. The contrast of hue stays; the fight goes out of it.
Going further
- Split complementary softens this harmony by splitting the opposite in two; Color harmonies explains all five.
- RYB: mixing paint and Color wheel explain the painter's wheel the angles are measured on.
- Books: Michel Eugène Chevreul, The Principles of Harmony and Contrast of Colours; Johann Wolfgang von Goethe, Theory of Colours; Josef Albers, Interaction of Color.