The primary colors are red, yellow and blue. These are the three pigment colors that cannot be mixed or formed by any combination of other colors. All other colors are derived from these three hues. But why is yellow considered a primary color while green is not? This article will examine the reasons behind this.
Definition of Primary Colors
Primary colors are the most basic colors. They cannot be created by mixing other colors together. In art and design, the primary colors are:
– Red
– Yellow
– Blue
These primary colors create secondary colors when mixed together. For example, mixing red and yellow makes orange, mixing blue and yellow makes green, and mixing red and blue makes purple.
So all other colors stem from some combination of the primary colors. But why these specific three colors and not others?
Light vs. Pigment Primaries
There are two different sets of primary colors – those in light and those in pigment.
Light primaries are red, green and blue (RGB). When light of these three colors overlap, they create all the other colors in the visible light spectrum. Televisions and computer monitors use combinations of red, green and blue light to produce color images.
Pigment primaries are red, yellow and blue (RYB). Pigments are substances that reflect certain wavelengths of light and absorb others. When different pigments are mixed together, they create new colors by reflecting combined wavelengths. Paints, inks, crayons and other color media use pigment mixtures to create various hues.
So why is yellow considered a primary pigment color while green is not? It has to do with the nature of light and pigments.
Why Yellow and Not Green?
There are a few key reasons why yellow is included as a primary color for pigments rather than green:
1. Yellow is a pure hue that cannot be mixed
Yellow pigment reflects light purely in the yellow wavelength. There is no way to mix other pigments together to create pure yellow – it can only be found in a pure yellow pigment.
2. Green can be created by mixing blue and yellow
While green is a secondary color in light, when it comes to pigments, green can easily be created by mixing blue and yellow pigments together. So green does not need to be a primary color.
3. Yellow has a broader wavelength range
The range of wavelengths that yellow pigment reflects is broader than that of green pigment. Yellow encompasses hues from lemon yellow to olive green. This broader wavelength range makes it a more versatile primary that can create more mixtures.
4. Yellow is stable while green is not
Over time, green pigments tend to fade, turn brown or otherwise transform. Yellow pigments are more colorfast and stable over the long term. As a primary color, stability is important.
| Primary Color | Wavelength Range |
|---|---|
| Red | 700-635 nm |
| Yellow | 635-570 nm |
| Blue | 470-435 nm |
This table shows the broad wavelength range that yellow pigment encompasses compared to red and blue. The breadth of yellow allows it to mix with the other primaries to form a wide array of secondary and tertiary hues.
Green as a Secondary Color
While green is not a primary color in the RYB pigment model, it has an important place as a secondary color.
Green sits between yellow and blue on the visible spectrum. When these two primary pigments are mixed, they produce the secondary color green.
The exact hue of green depends on the specific yellow and blue pigments used and their proportions. Mixing a lemon yellow and phthalo blue produces a bright green. An olive yellow and cobalt blue makes a more muted green. Viridian green pigment is commonly used as a vivid green pigment.
So even though green pigment cannot be a primary, it has a very significant role in color mixing. Its position between warm yellow and cool blue makes it incredibly versatile for painting nature, landscapes and color combinations.
Other Color Models
While RYB is the standard set of primary colors for pigments, there are other alternative color models.
Cyan, magenta and yellow (CMY) are the primary colors used in color printing. Cyan and magenta are cooler versions of blue and red, while yellow remains the same. When mixed together, these three colors can create a full spectrum of hues in ink and print.
Cyan, magenta, yellow and black (CMYK) is an expanded printing model. The addition of black allows for better control of tone, shading and mixing dark colors.
There are also models that use the primary colors of light – RGB (red, green, blue) and RGV (red, green, violet). While these three-color systems work for light and video, they are not practical for mixing physical pigments.
So in summary, the standard RYB system is designed specifically around creating the widest array of hues from primary pigments. And yellow differentiated itself as the necessary third primary color rather than green.
Conclusion
Yellow is considered a primary color for pigments while green is not due to inherent properties of the two hues. Yellow has a uniquely broad wavelength range that no mixture can replicate. Green, on the other hand, can easily be created by mixing yellow and blue pigments. Additionally, yellow offers stability while green pigments tend to transform over time.
The RYB primary model allows the creation of a complete spectrum of colors for paints, inks, dyes and other pigmented media. While green holds an important secondary position, yellow established itself as the necessary third primary after red and blue due to its singular nature. So the next time you pick up a crayon box with yellow but no green, remember the fascinating optics and physics that determine the primacy of yellow on the artist’s palette.