A quick note on spelling before anything else, because it trips people up constantly. The word is complementary, with an e — colors that complete each other. Complimentary with an i means free of charge, or saying something nice. Search engines see enough of both that you will find this page either way.
What complementary colors are
Two colors are complementary when they sit directly opposite each other on the color wheel. On the standard twelve-part artist's wheel that gives you three pairs, each one a primary against the secondary mixed from the other two primaries:
- Red and green
- Blue and orange
- Yellow and violet
Because the wheel keeps subdividing, the tertiary colors pair off the same way — yellow-orange against blue-violet, red-orange against blue-green, yellow-green against red-violet. The rule holds however finely you slice it: whatever is opposite is the complement.
If you would like the underlying structure first, our guide to the color wheel lays out primaries, secondaries and tertiaries before you start pairing them.
Why they matter
Two reasons, and they pull in opposite directions.
Side by side, complements intensify each other. Put a red next to a green and both look more saturated than either does alone. Nothing about the pigment has changed. Your eye has adjusted, and the effect is called simultaneous contrast. This is why a sunset painting with a blue-gray sea reads as more fiery than a sunset painting with a warm sand foreground.
Mixed together, complements cancel each other. Stir a little red into a green and you get a duller green. Keep going and you reach a neutral gray-brown. This is the single most useful fact in practical color mixing, because it means you can gray a color down without adding black, which kills it. It is also why the shadow colors in a well-designed kit are so often a muddied version of the object's own complement rather than a gray from the tube.
Split complementary schemes
A split complementary scheme takes a base color, finds its complement, and then uses the two colors sitting either side of that complement instead of the complement itself.
So if your base is green, the complement is red, and the split pair is red-orange and red-violet. If your base is blue, the complement is orange, and the split pair is yellow-orange and red-orange.
You still get the contrast, because both of those colors are still roughly opposite your base. What you lose is the hard vibrating edge that a true complementary pair produces at full saturation. It is the scheme most illustrators reach for when they want energy without tension.
Triadic schemes
A triadic scheme uses three colors spaced evenly around the wheel — every fourth position on a twelve-part wheel. Red, yellow and blue is one. Violet, orange and green is another. Blue-violet, yellow-green and red-orange is a third.
Triads are lively and balanced, and they are also the easiest scheme to overdo. The convention that makes them work is to pick one of the three as the dominant color, use the second sparingly, and let the third appear only as accents. Three colors at equal strength across a canvas has no hierarchy, and the eye does not know where to go.
What simultaneous contrast actually does
The rules here are frequently mangled, so it is worth stating them carefully. Everything below is about how a color appears, not about what is in the pot.
- A color placed against its complement looks more saturated.
- A color placed against a neighbor on the wheel looks less distinct, because there is little to push against.
- A light color against a dark one looks lighter, and the dark one looks darker. Contrast in value exaggerates itself.
- Two colors of similar value and similar saturation sitting together both look duller, and the boundary between them goes soft.
- A neutral gray placed next to a strong color takes on a hint of that color's complement. A gray beside a red will read faintly green.
- A warm color looks warmer beside a cool one, and the cool looks cooler still.
Two paintings worth looking at
Van Gogh's Café Terrace at Night is built almost entirely on blue against orange. The awning and the lit terrace are warm, the sky and the street beyond are deep blue, and the picture feels bright and sociable because the two halves are pushing on each other.
The Night Café, painted the same year, uses red against green and feels like the opposite. Writing to his brother Theo, Van Gogh described the picture as a clash and contrast of the most disparate reds and greens, and said he had tried to express the terrible passions of humanity through those two colors. He also called it one of the ugliest things he had made, which tells you he knew exactly what he was doing.
The two paintings use the same device and land in completely different places. That is the point worth taking away: complementary contrast is a volume control, not a style. If you like his work, we have written more about Van Gogh's Starry Night.
J.M.W. Turner's The Slave Ship does the same thing on a larger scale, with a burning orange sky above a cold blue-green sea. The sky is not painted any more brightly than it would be on its own. The sea is what makes it burn.
Using this on a numbered canvas
On a paint by numbers kit the color decisions have already been made, which sounds like it makes color theory irrelevant. It does the opposite: it gives you a finished example to read.
Next time you open a kit, lay the paint pots out and look for the pairs. On a sunset design you will almost always find a warm orange or pink sitting against a cool blue or violet. On an autumn scene you will find oranges against the blue of water or sky. Those pairings are why the finished canvas has life in it, and noticing them is how you start to see color the way the artist did.
Two practical things follow from it. First, resist the temptation to substitute a color you like better — pulling one half of a complementary pair collapses the effect the whole design was built on. Second, if two adjacent sections look wrong to you while you are painting, wait until the surrounding areas are filled in before deciding. A color judged against bare white canvas tells you nothing about how it will look against its neighbors.
Testing before you commit
If you are mixing your own colors rather than working from a kit, test them next to each other and not in isolation. A swatch on white paper is a different color from the same paint surrounded by its neighbors, which is the whole lesson of this page. Let acrylic dry before you judge it too, because it darkens very slightly as the binder clears.
If you want to see color relationships worked out at full size, the designs in our kit collection are all licensed original paintings, and our guide to blending on a numbered canvas covers what happens where two of those colors meet.
