Red, blue, and green are considered the primary colors in additive color systems like computer monitors and TV screens. However, in subtractive color systems like painting and printing, the primary colors are typically considered to be red, yellow, and blue. So whether red, blue, and green are all primary colors depends on the specific color system being used.
Additive vs. Subtractive Color Systems
There are two main types of color systems:
Additive Color Systems
In additive color systems like computer and TV displays, light is emitted to create color. Red, green, and blue light are mixed in different proportions to create all the colors we see on screens. For example:
| Red light | + | Green light | = | Yellow light |
| Red light | + | Blue light | = | Magenta light |
| Green light | + | Blue light | = | Cyan light |
In additive color systems, red, green, and blue are considered the primary colors because all other colors can be created by mixing those three colors of light.
Subtractive Color Systems
In subtractive color systems like painting, inks, and dyes, colors are created by absorbing or subtracting certain wavelengths of light. The primary colors in subtractive systems are typically considered to be red, yellow, and blue. For example:
| Red paint | + | Yellow paint | = | Orange paint |
| Yellow paint | + | Blue paint | = | Green paint |
| Blue paint | + | Red paint | = | Purple paint |
In subtractive systems, red, yellow, and blue are considered the primary colors because in theory all other colors can be created by mixing those three pigments.
So in summary, additive and subtractive color systems have different primary colors:
| Additive (RGB) | Subtractive (RYB) |
|---|---|
| Red | Red |
| Green | Yellow |
| Blue | Blue |
The CMYK Color Model
There is another common subtractive color model that uses cyan, magenta, yellow, and black (CMYK) as its primary colors. This is the system used in color printing.
Cyan, magenta, and yellow are considered the main primaries. But black ink is added for better contrast and to create true blacks.
For example, here is how secondary colors are created by mixing CMYK primaries:
| Cyan | + | Magenta | = | Blue |
| Cyan | + | Yellow | = | Green |
| Magenta | + | Yellow | = | Red |
The CMYK model is considered more practical for real-world printing than RYB because combining cyan, magenta, and yellow pigments can create a reasonable approximation of black. RYB primaries would produce a muddy brown when combined.
So in the CMYK system, the primary colors are cyan, magenta, yellow, and black. Red, green, and blue are not primary colors in this model.
Light Primaries vs. Pigment Primaries
As demonstrated above, additive and subtractive color systems have different primary colors. This is because of key differences between mixing light versus mixing pigments:
Light Primaries
– In additive color mixing, combining primary lights creates secondary colors by addition of wavelengths. All wavelengths together produce white light.
– The primary lights in additive systems are red, green, and blue. These directly correlate to the three types of color receptors in our eyes.
– Computer screens, TVs, projectors, and other displays use the RGB additive primaries to create color.
Pigment Primaries
– In subtractive color mixing, combining paints, dyes, or inks creates secondary colors by absorbing or subtracting wavelengths. All pigments combined produces black.
– The primary pigments depend on the specific subtractive system. RYB and CMYK are common sets of subtractive primaries.
– Paints, dyes, inks, and other physical color technologies use subtractive primaries. Which set is used depends on the specific context and desired results.
So in summary, additive RGB systems have red, green, and blue as primary colors, while subtractive CMYK and RYB systems have different primary colors based on practical pigment mixing.
Other Color Models
Beyond RGB, CMYK, and RYB, there are other color models that have their own set of primary colors:
– HSV (Hue, Saturation, Value) – The primaries are hue, saturation, and value/brightness. Hue determines color shade, saturation is the vibrancy, and value sets how light or dark the color is.
– HSL (Hue, Saturation, Lightness) – Similar to HSV, with hue, saturation, and lightness as primaries. Lightness replaces value.
– YIQ – Used in NTSC television broadcasting. The primaries are luma (brightness), in-phase, and quadrature.
– YPbPr – Used in analog component video. The primaries are luma, blue difference, and red difference signals.
– XYZ – Based on human perception of color. The X, Y, and Z primaries correspond to the three different color receptors in the human eye.
So while red, green, and blue are primary colors in the RGB space, other color models use entirely different primary colors based on other properties of light and color perception.
Traditional Artist Primaries
Traditional art has its own primary colors that differ from modern color theory:
– Cyan, yellow, magenta – Pre-19th century painters traditionally used cyan blue, yellow, and magenta red as primaries for pigment mixing.
– Vermilion, yellow ochre, ultramarine – Later more practical pigments made vermilion, yellow ochre, and ultramarine the common primaries for mixing paints.
– Cadmium yellow, alizarin crimson, ultramarine blue – By the 20th century, synthetic pigments made cadmium yellow, alizarin crimson, and ultramarine blue the preferred primary palette.
So historically, painters used their own traditional primary pigments based on available materials and practical color mixing. These differed greatly from the primaries used in modern color theory.
Primary Color Requirements
For a set of colors to be considered primary colors, they generally must meet a few key criteria:
– The primaries can be mixed to create a wide range of secondary and intermediate colors. In theory, all colors can be created from mixing the primaries.
– The primaries cannot be created by mixing other colors in the system. Primary colors are the basic building blocks of that color model.
– The primaries are distinct from each other. There is no overlap or redundancy between each primary color.
– The primaries relate directly to human color perception. At least three primaries relate to the three types of color receptors (cones) in our eyes.
Not all color models meet these requirements perfectly. But in general, primary colors aim to be a small set of distinct colors that can mix to create all other colors in that system.
Conclusion
In summary, whether red, blue, and green are considered primary colors depends on the specific color model:
– In the additive RGB model, red, green, and blue are primary colors. This model is used for light-emitting devices like computer displays.
– In the subtractive CMYK model, cyan, magenta, yellow, and black are the primary colors. This model is used for reflected light like printing inks.
– Other color systems like RYB, HSV, XYZ, etc. each have their own primary colors based on that model’s goals and limitations.
So while red, green, and blue are key primaries for light and displays, other color systems do not consider them the definitive set of primary colors. Color theory provides a variety of valid ways to define primary colors. The “correct” primaries depend on the specific application and technology.
