When red and blue are combined together, they make the color purple. This happens because red and blue are considered primary colors in the additive color model, along with green. When you mix the primary colors together in pairs, they make the secondary colors – purple, orange, and green.
Additive vs. Subtractive Color Models
There are two main color models that are used to understand how different colors interact with light – the additive color model and the subtractive color model. The additive color model deals with light itself, while the subtractive model deals with pigments and dyes. This difference affects what happens when colors are mixed.
In the additive color model, red, green, and blue are the primary colors. This is because these are the primary colors of light. When you combine red and green light, it makes yellow light. When you combine green and blue light, it makes cyan light. And when you combine red and blue light, it makes magenta light. Magenta is the same color as purple for all intents and purposes.
In the subtractive color model, the primary colors are cyan, magenta, yellow, and black. This is because paints, inks, and dyes work by absorbing certain wavelengths of light and reflecting others. When you combine cyan, magenta, and yellow paints or dyes together, they absorb all wavelengths of light and produce black.
Why Red and Blue Make Purple
When we talk about mixing red and blue, we are working with light and the additive color model. Red light and blue light are both primary colors of light. When you shine red light and blue light onto the same spot, the light sensors in your eyes receive both red wavelengths of light and blue wavelengths of light at the same time. Your visual system interprets these combined wavelengths as the color purple.
At the particle level, red light is made of photons with wavelengths around 700 nm, while blue light is made of photons with wavelengths around 435 nm. When these photons hit your eyes at the same time, your eyes cannot tell them apart. The combined effect is that your eyes see the color purple, which sits between red and blue in the color spectrum.
How the Purple Color is Perceived
The specific shade of purple that you see when you mix red and blue depends on the intensities of the original colors. Mixing a bright primary red and a darker primary blue will result in a purple that is closer to red. Mixing a darker red and brighter blue will result in a purple closer to blue. Mixing equal intensities of primary red and blue makes a vivid shade halfway between the two.
The human eye actually has receptor cells called cones that detect different wavelength ranges of light. There are cones for long wavelength red light, medium wavelength green light, and short wavelength blue light. Purple light stimulates the red cones and the blue cones at the same time without stimulating the green cones very much. This pattern of stimulation is interpreted by the brain as the color purple.
Other Ways to Make Purple
Combining red and blue light is not the only way to make the color purple. Here are a few other ways purple can be made:
- Mixing magenta and blue light or paints. Magenta is a primary color next to red on the color wheel.
- Mixing red and violet light or paints. Violet is a spectral color between blue and purple.
- Combining blue and a smaller amount of red light or paint.
- Combining purple dye with a white material like paper or fabric.
Any process that results in a pigment, dye, or light wavelength that stimulates both the red and blue color receptors in your eyes will produce a shade of purple.
Examples of Purple in Nature
In nature, purple is relatively rare compared to other major colors like green, blue, yellow, orange, red, and brown. There are not many natural pigments that absorb light in the blue to red wavelength range. Some examples of natural purple colors are:
- Purple majesty potatoes – these potatoes get their pigment from antioxidants called anthocyanins.
- Purple carrots – these contain pigments called anthocyanins.
- Eggplant skins – the purple pigment is called nasunin.
- Purple sweet potatoes – pigments include anthocyanins.
- Purple grapes and purple berry fruits – the anthocyanin pigments act as antioxidants.
- Hydrangeas – can be purple due to soil acidity affecting pigment molecules.
- Purple passionflowers – contain anthocyanin pigments.
- Violets – contain anthoxanthin pigments.
- Purple butterflies – structural color from light interference.
As you can see, a common source of natural purple pigment comes from anthocyanin molecules. These molecules reflect red and blue light simultaneously, allowing plants to take advantage of the antioxidant properties of anthocyanins while displaying a visually striking color.
Shades and Variations of Purple
There are many possible shades, tints, and tones of purple besides the primary reddish-blue purple described above. Some variations include:
- Violet – A spectral color with more blue than red. Violet light has a wavelength of about 380-450 nm.
- Mauve – A pale, dusty purple with more red or pink tones. Similar to lavender.
- Lilac – A light purple with more blue tones.
- Wisteria – A medium purple named after the flowering wisteria vine.
- Orchid – A medium purple that matches some orchid flowers.
- Amethyst – A deeper purple, sometimes with red-blue flashing tones.
- Byzantium – A darker purple-red associated with the Byzantine Empire.
- Tyrian purple – An ancient reddish-purple dye made from sea snails.
- Veronica – A deep blue-purple named after the veronica flower.
Tints of purple add white to make soft pastel shades like lavender and lilac. Tones of purple involve gray for muted shades. And shades of purple add black for deep rich variations.
Uses and Symbolism of the Color Purple
Here are some of the common uses, meanings, and symbols associated with the color purple:
| Use/Meaning | Description |
|---|---|
| Royalty | Purple has long been associated with royalty, nobility, luxury, and ambition. The rarity and expense of purple dyes in ancient times helped cement this association. |
| Wealth | Purple can symbolize wealth, riches, extravagance, and affluence in material goods. |
| Wisdom | As a balance of red passion and blue calm, purple can represent wisdom, spirituality, ingenuity, and creative thinking. |
| Creativity | Purple evokes creative thinking, originality, imagination, and nonconformity. |
| Mystery | The rarity of purple in nature adds an air of mystery and mystique. |
| Magic | Purple is strongly associated with fantasy, magic, wizardry, and spiritualism. |
Purple is a popular color in fiction, fantasy, art, fashion, decor, and architecture. It tends to stand out and grab attention while also conveying complexity.
Mixing Paint, Light, and Dyes
The exact process of combining colors to make purple depends on whether you are working with paints, light sources, fabric dyes, or digital media:
- Paints – Mix a primary or secondary red paint with a primary or secondary blue paint. Start with small amounts and adjust the proportions until you achieve the desired purple.
- Light – Shine a red light source and a blue light source onto the same area. Overlap the beams to form purple.
- Dyes – Combine a red dye bath and a blue dye bath, then immerse the fabric. Or start with purple dye. The intensity depends on the dye concentrations.
- Digital – Use RGB color sliders in a program to combine high blue values and high red values. Tweak other colors like green to perfect the purple.
Always start with small amounts and do tests when mixing paints and dyes. It takes experience to get the exact purple you want.
Conclusion
In summary, mixing red and blue makes purple because red and blue are primary colors of light. When red and blue wavelengths of light enter your eyes simultaneously, the light receptors in your eyes and color-processing vision system perceive this combination as the color purple. The specific shade of purple depends on the relative intensities of the red and blue components. Purple sits halfway between red and blue on the visible color spectrum.
