Yellow and blue are considered complementary colors in color theory. When mixed together in the right proportions, they produce neutral gray. This leads to the common notion that yellow and blue are “inverses” of each other. But what exactly does it mean for two colors to be inverses? Here we’ll examine the origins of this idea and look at the visual and mathematical relationships between yellow and blue.
Complementary Colors
The concept of complementary colors originated in the 18th century when Johann Wolfgang von Goethe studied the afterimages that appear after staring at a color. He noticed that the afterimage tended to be in hues opposite from the original color on the color wheel. For example, staring at blue produced a temporary yellow afterimage. This complementary color phenomenon was likely related to the opponent process theory of color vision. The human eye contains receptors sensitive to red, green, and blue. Staring at one color fatigues those receptors while the receptors for the opposite color remain active, resulting in the complementary afterimage. This was the beginning of the idea that color pairs like yellow and blue somehow go together.
Later work by Ogden Rood expanded on this. He systematically charted colors and their complements on a color wheel. He found that complementary colors were located directly across from each other. Mixing complementary colors produced a neutral gray or white. This reinforced the idea that complementary colors balance each other out in some way.
Additive vs. Subtractive Color Mixing
To understand if yellow and blue are truly inverses, we need to consider how they mix both in light and in pigment.
Additive Color Mixing
Additive color mixing refers to mixing colored light sources. In RGB color models, red, green, and blue light are combined to create most colors. Mixing blue and yellow light together produces white light.
| Color | Red | Green | Blue |
|---|---|---|---|
| Yellow | 1 | 1 | 0 |
| Blue | 0 | 0 | 1 |
| Mix | 1 | 1 | 1 |
This demonstrates that additively, yellow and blue are not exact inverses. Instead, their combination contains the full spectrum of light.
Subtractive Color Mixing
Subtractive color mixing refers to mixing pigments. In CMYK color models, cyan, magenta, and yellow pigments are combined to absorb and subtract certain wavelengths of light. Mixing blue and yellow pigments together produces a neutral dark gray or black:
| Color | Cyan | Magenta | Yellow |
|---|---|---|---|
| Yellow | 0 | 0 | 1 |
| Blue | 1 | 1 | 0 |
| Mix | 1 | 1 | 1 |
Here we see evidence that subtractively, yellow and blue act as inverses, combining to block all light from being reflected or transmitted.
Perceptual Effects
Beyond color theory, yellow and blue also have complementary perceptual effects. Warm yellows are energetic and eye-catching. Cool blues are calming and receding. Using yellow on a blue background helps the yellow jump out. Blue writing is easier to read on yellow paper. This complementary enhancement occurs because the colors stimulate the eye in opposite ways.
Mathematical Relationship
We can also examine how yellow and blue are related mathematically. In the RGB color model, yellow and blue are inverses in the sense that yellow contains the colors red and green while blue is solely blue. Mixing yellow (red + green) with blue (just blue) attempts to produce white (red + green + blue).
However, in the more common CMYK model, yellow and blue are defined differently. Yellow is the absence of blue, while blue is the absence of yellow. Mixing them produces black, the absence of all color. Mathematically speaking then, yellow and blue are more direct inverses in the CMYK model.
Conclusion
While yellow and blue are complementary colors and mixing them produces gray, they are not perfect mathematical inverses. Additively, they produce white light rather than cancelling each other out. Only in subtractive CMYK color mixing do they truly act as inverses, creating black by blocking all reflected light when combined. However, their perceptual differences and opposing effects on the human eye do align with the idea of them being visual inverses. So while not a perfect inversion, yellow and blue are certainly strong complements.
