This is a common misconception that many people have – that mixing the colors blue and yellow will result in the color green. However, this is not actually the case. The real reason blue and yellow do not make green has to do with the science of how color works.
The Basics of Color Theory
In order to understand why blue and yellow don’t make green, it’s important to first understand some basics about color theory. The colors we see are a result of reflected light. Objects absorb some wavelengths of light and reflect others – the wavelengths that are reflected are what we perceive as color.
There are three primary colors of light: red, green and blue. By mixing different amounts of these three colors, all other colors can be made. This is known as the additive color model. For example, mixing red and green light makes yellow light. Mixing all three primary colors of light together makes white light.
When it comes to pigments, dyes and inks – like paints or crayons – things work a little differently. With pigments, we use the subtractive color model. The primary colors are cyan, magenta and yellow. When these pigments are mixed together, they absorb some wavelengths and reflect others, creating new color combinations.
Why Blue and Yellow Don’t Make Green
So why don’t blue and yellow make green when mixing paints or other pigments? It comes down to the difference between additive and subtractive color models.
In the additive (light) model, blue and green are primary colors. Mixing blue and yellow light together makes white light, not green light. But when working with pigments, blue and yellow are not primary colors. Instead, the primary colors are cyan, magenta and yellow.
Cyan absorbs red light and reflects blue and green. Yellow absorbs blue light and reflects red and green. When cyan and yellow pigments are mixed, both red and blue light get absorbed, while green is the only wavelength that gets reflected back to our eyes. Therefore, mixing cyan and yellow makes green.
Blue pigment doesn’t contain cyan – it contains particles that only reflect blue light. Mixing it with yellow pigment means the blue still gets absorbed, and only yellow light gets reflected back. So blue and yellow pigments combined make a yellowish color, not green.
The Difference Summarized
Here is a table summarizing the key differences between the additive (light) and subtractive (pigment) color models:
| Color Model | Primary Colors | Secondary Colors |
|---|---|---|
| Additive (Light) | Red, Green, Blue | Cyan, Magenta, Yellow |
| Subtractive (Pigment) | Cyan, Magenta, Yellow | Red, Green, Blue |
As you can see, the primary and secondary colors are reversed between the two models. This explains why mixing blue and yellow light makes white light, while mixing blue and yellow pigments makes a yellowish color.
The Scientific Explanation
We can go a little more in-depth scientifically to explain what happens when blue and yellow pigments are combined.
As explained above, blue pigment reflects only blue light. The specific wavelengths of light reflected by blue pigment are around 450-495 nanometers.
Yellow pigment reflects red, orange and green light. The wavelengths reflected are roughly 570-590 nanometers (red) and 495-570 nanometers (green).
When these two pigments are mixed together, the blue pigment continues to reflect its 450-495nm blue light, but the yellow pigment absorbs the blue instead of reflecting it. The yellow pigment still reflects the longer red and green wavelengths of 570-590nm and 495-570nm. The combination of these wavelengths produces a yellowish-green color, not a true green.
How to Make Green from Blue and Yellow
Now that we understand why combining blue and yellow pigments doesn’t make green, how can green actually be made from blue and yellow? Here are two options:
- Start with cyan as your blue. Mixing cyan pigment with yellow will absorb red and reflect green.
- Start with blue light instead of pigment. Mix blue light with yellow light to make green light.
For crafters and artists, opting to use cyan rather than blue paint is the easiest route to mix green from primary colors. Cyan is one of the primary colors in the subtractive model, so when combined with the other primary, yellow, it will make the secondary color green.
Cyan pigment particles reflect both blue and green light. This means the green wavelength can still be reflected even when the blue gets absorbed by the yellow pigment. The result is green light that gets reflected back to our eyes.
The Psychological Component
Interestingly, the expectation that blue and yellow should make green may stem from psychological factors as well. The brain likes to categorize groups of three when processing colors. Since the primary colors in the additive model are red, green and blue, there is an instinctive expectation that the secondaries derived from those primaries will be cyan, magenta and yellow to complete the triad.
But since cyan and blue look similar, our brains can incorrectly lump them into the same category. We still gravitate towards the pattern of primaries and secondaries in groups of three, leading to the false assumption that blue and yellow must make green.
In reality, while red and green are definite primaries in both models, blue is only a primary in light, while cyan takes its place as the third primary for pigments. Understanding this distinction is key to unraveling the myth that blue and yellow pigments can create the color green.
Conclusion
The notion that you can mix blue and yellow to make green is a very common misconception rooted in an oversimplification of color theory. While combining blue and yellow light will produce green light, pigments do not work the same way. Blue pigment reflects only blue wavelengths, and yellow pigment reflects red and green but absorbs blue. The combination results in a yellowish color, not true green.
To make green from primary color pigments, you need to start with cyan (which reflects both blue and green) as your blue source instead of plain blue pigment. The cyan combined with yellow will absorb red and reflect the green wavelengths. Understanding the intricacies of additive and subtractive color models explains why mixing blue and yellow pigments won’t give you the color green that you might expect.
