When most people first learn about mixing colors in art class, they are taught that the primary colors are red, yellow, and blue. They are often told that if you mix the primary colors together, you will get secondary colors – mixing red and yellow makes orange, red and blue makes purple, and blue and yellow makes green. However, many are surprised to find that if you mix all three primary colors together, rather than getting black as some expect, you actually get brown. This can seem counterintuitive at first, so why does combining the primary colors red, yellow, and blue actually make brown?
The Basics of Color Mixing
To understand why mixing the primary colors makes brown, it helps to review some basics about color and light. The primary colors are called primary for a reason – they are colors that cannot be created by mixing other colors. Instead, all other colors are derived from some combination of the primary colors.
This is because of the nature of light. Light visible to the human eye contains wavelengths across the visible spectrum, from red wavelengths around 700nm to violet wavelengths around 400nm. Our eyes have receptors that are sensitive to three main regions of this spectrum – long wavelengths we see as red, medium wavelengths we see as green, and short wavelengths we see as blue. When light contains a combination of these wavelengths, our eyes and brain interpret it as a blended color.
So in theory, all possible colors can be created by mixing appropriate amounts of red, green, and blue light. This is known as the additive color model. Pigments like paints or dyes work by absorbing certain wavelengths and reflecting the rest back to our eyes. So with pigments, you start with a white surface that reflects all light equally, and color is created by selectively absorbing wavelengths. The primary pigment colors of red, yellow, and blue align with absorbing blue/green, blue, and red light respectively.
Why Red, Yellow and Blue are Considered the Primary Colors
Given the nature of light and color, why are red, yellow and blue considered the primary colors? Wouldn’t red, green, and blue make more sense based on the light spectrum?
The reason has to do with the history of color theory and pigments. When color theory was first developed, paintings used pigments rather than emitted light. There were no affordable blue pigments available. Most blue paints were made with rare lapis lazuli, making them extremely expensive. Without readily available blue paint, 18th century color theorists like Thomas Young and Hermann von Helmholz designated red, yellow, and blue as the primary colors since they were the most common and affordable pigments.
These primaries align well with a subtractive color model. Combining paints does selectively absorb more wavelengths, moving towards black. Red paint absorbs green and blue, yellow absorbs blue, and combining them absorbs mostly blue and green, leaving red and giving brown.
While red, green, and blue may be more accurate primary colors, red, yellow, and blue remain the traditional primary colors used by most artists and for education. The tradition holds even though modern paints have made other pigments widely available.
The Properties of Red, Yellow, and Blue Pigment
Part of the reason red, yellow, and blue have endured as primary colors comes down to their unique properties as pigments. Each pigment absorbs a different portion of the visible light spectrum:
- Red pigment absorbs wavelengths around 500-570nm, the green portion of the spectrum.
- Yellow pigment absorbs wavelengths around 400-470nm, the violet and blue portion of the spectrum.
- Blue pigment absorbs wavelengths around 620-700nm, the orange and red portion of the spectrum.
When combined together, red, yellow, and blue pigments absorb most visible wavelengths of light, removing most color and reflection and resulting in a dark brown or near-black.
In contrast, green pigment reflects green and yellow light while absorbing blue and violet. This overlaps significantly with yellow pigment. Violet pigment is rarely used since blue absorbs orange/red wavelengths. So red, yellow, and blue have uniquely broad absorption across the spectrum.
The Mixing Process Step-By-Step
Now let’s walk through the process of mixing red, yellow, and blue paint step-by-step to see how the blending of the pigments produces brown:
- Start with a white surface like paper or canvas that evenly reflects all visible light wavelengths.
- Add red paint. This absorbs green and blue light, reflecting back mostly red wavelengths around 650nm.
- Add yellow paint. This absorbs violet and blue wavelengths around 400-470nm. The overlap with red absorbs more green light.
- The combination of red and yellow reflects back mostly red and orange light, absorbing greens and blues. To our eyes this mixes to look orange.
- Add blue paint. Blue absorbs the red end of the spectrum. This absorbs most of the remaining light, leaving a very dark brown that appears near black.
- Some violet and orange light is still reflected, keeping it from appearing completely black. But to our eyes, the heavily blended combination of all three primary paints appears as a dark brown.
We can see that as more primary paint colors are mixed together, more and more of the visible spectrum is absorbed. The increasing blend absorbs more wavelengths until most light is absorbed, giving the color brown.
The Role of Pigment Color Biases
Another factor that contributes to mixing the primaries giving brown has to do with the inherent biases of pigments. Paints and dyes do not reflect light evenly across the spectrum, even if they appear red, yellow or blue to our eyes. Many have biases towards certain wavelengths.
For example, common blue pigments like ultramarine or phthalocyanine blue reflect some violet and green biases. This enhances their blue appearance. But when mixed with red and yellow pigments, those extra reflections are quickly absorbed, contributing to the muddy dark brown.
Similarly, many red and yellow pigments reflect a bit of extra green and orange light respectively. These reflections also get absorbed when mixing, increasing the perception of brown. Pigments with purer, more narrow reflections would mix together differently. But commercially available paints use pigments with impure reflections that skew brown when combined.
The Effect of Different Proportions
The exact hue and lightness of the brown produced by mixing primaries also depends on the specific proportions of the red, yellow, and blue paint used. Mixing equal amounts gives the darkest brown approaching black. But changing the ratios results in lighter, more colorful browns.
For example, using more yellow gives a golden brown tone. More blue contributes a colder, grayer brown. Higher red ratios create warmer, orange-tinged browns. The table below shows some example brown colors created by different primary paint ratios:
| Red | Yellow | Blue | Mixed Color |
|---|---|---|---|
| 1 part | 1 part | 1 part | Dark charcoal brown |
| 3 parts | 1 part | 1 part | Reddish, warm light brown |
| 1 part | 3 parts | 1 part | Golden tan brown |
| 1 part | 1 part | 3 parts | Cool gray-brown |
So the specific hue of brown can be tweaked by changing the mixing ratios, though any combination eventually trends towards a muddy brown since all wavelengths are being absorbed.
Examples of Brown Pigment Mixing
To further demonstrate these color mixing principles, here are some real examples of mixing common red, yellow, and blue paint pigments:
- Mixing cadmium red, cadmium yellow, and ultramarine blue acrylic paint produces a very dark muddy brown.
- Combining magenta, yellow oxide, and phthalo blue oil paints creates a rich blackish-brown.
- Blending alizarin crimson, lemon yellow, and cobalt blue watercolor yields a deep brownish-black.
- Mixing together two primaries like hansa yellow and phthalo blue makes a nice olive green. Adding in any red such as cadmium red medium then quickly grays and darkens the mix into a brown.
As described, adding increasing amounts of the primary red, yellow, and blue pigments absorbs more light wavelengths, progressively darkening towards brown. Mixing all three absorbs so much of the spectrum that mostly browns will result.
Light vs. Pigment Primaries
Now that we’ve explored pigment mixing, what about mixing light instead of paint? As mentioned earlier, the primary colors of light are red, green, and blue, not red, yellow, and blue.
Mixing beams of pure red, green, and blue light does produce white rather than brown. This is because light mixing is additive, so combining wavelengths across the spectrum gives white light, not darkened colors.
However, real light sources like LED sets often have impure color biases, just like pigments. Mixing impure red, green, and blue stage lights still often ends up with a dingy yellow-brown tone. So even with emitted light, underlying biases can still mix additively into brownish tones.
Color Mixing in Digital Media
Modern digital color mixing uses the RGB or red, green, blue additive model. Digital image formats and screen pixels combine R, G, and B components to display full-spectrum color.
Mixing pure RGB colors does correctly give shades of gray from white to black. But again, real RGB color representations have inherent biases in their spectral distributions. For example, the RGB definition of “blue” has significant green and red components. This causes impure RGB primaries to also mix towards brown.
Look at mixing pure hex RGB colors FF0000 red, FFFF00 yellow, and 0000FF blue:
| Red | Green | Blue | Mixed Color |
|---|---|---|---|
| FF0000 | FFFF00 | 0000FF | #7F2F0F – Medium brown |
The impurities and overlap in the R, G, and B definitions still blend towards a muddy brown compared to theoretical perfect primaries. But blending pure light or pigments with perfect narrow spectral absorption would not make brown.
Cultural Associations with Brown
Beyond the technical side of mixing colors, cultural associations also contribute to brown seeming like an “ugly” and unsophisticated color. Brown is very common in nature – soil, tree bark, rocks – but uncommon in vivid flowers, animals, or foods. Similarly, many synthetic browns come from mixed waste and dirtiness – mixing all paint together as a child, dark muddy water, etc.
These mundane and dirty associations lead brown to be considered a boring color, especially compared to bright primary colors on their own. Brown is the color of gradients between other more saturated hues. It has connotations of diluting color and mixing the purity away. This further enhances the sense of brown being a color of blended muddiness.
Conclusion
When blending the primary colors of red, yellow, and blue, combining their light absorption properties results in a dark, muddy brown. This brown results from the increasing blending of the pigments absorbing wider ranges of the visible light spectrum together. The inherent biases and impurities in real pigment and light primaries enhance the perception of brown when mixing. So while idealized primary colors can mixadditively, real-world pigment and light mixing trends towards brown. This practical reality helps explain the brown color that results from mixing the primary paint colors red, yellow, and blue together.