The question of what colors make up violet has two distinct answers, depending on whether the discussion is about light or pigment. In the world of physics and light, the answer is straightforward and involves no mixing at all. However, in art and everyday experience, the color we often call “violet” is actually created by combining other colors. This confusion is common because the human brain interprets light and pigment mixtures in ways that blur the line between a pure color of light and a perceived color mixture.
The Scientific Answer: Violet as a Spectral Color
From a scientific perspective, violet is not made up of other colors; it is a pure, single color of light. It exists at the extreme short-wavelength end of the visible spectrum, meaning it is monochromatic light. This means the light consists of a single or very narrow band of wavelengths, rather than a combination of different ones. The human eye perceives violet when it detects light with a wavelength between approximately 380 and 450 nanometers (nm). When white light, such as sunlight, passes through a prism, the light separates into a rainbow of spectral colors through a process called refraction. Violet is the color that bends the most, positioning it next to blue and before the invisible ultraviolet radiation. The concept of violet as a pure color is fundamental to the physics of light. It is one of the colors that Isaac Newton identified when he first divided the spectrum of visible light.
The Difference Between Violet and Purple
The reason for the common misunderstanding about violet’s composition lies in its frequent confusion with the color purple. Violet is a spectral color that appears in the rainbow, while purple is what is known as a non-spectral color. This means no single wavelength of light corresponds to purple. Purple is a color the brain constructs when the eye receives signals from both the red (long-wavelength) and blue (short-wavelength) ends of the visible spectrum simultaneously. Crucially, the light mixture that creates purple contains very little or no intermediate green light. The brain interprets this unique combination of signals, which bypasses the central part of the spectrum, as the color purple.
Cone Cell Activation
The retina contains three types of cone cells: L-cones, M-cones, and S-cones, which are sensitive to long (red), medium (green), and short (blue) wavelengths, respectively. When viewing true spectral violet, only the S-cones are strongly stimulated, along with some slight activation of the L-cones. When viewing purple, both the L-cones and the S-cones are activated, while the M-cones remain relatively unstimulated. This difference in cone stimulation is why violet appears more bluish and less saturated, while purple tends to be perceived as more reddish. Purple is always a mixture of wavelengths, whether from two different light sources or from pigments, making it physiologically and physically distinct from the single-wavelength nature of spectral violet.
Creating Violet Look-Alikes with Pigments
In the world of art and printing, the color that closely resembles spectral violet is created using the subtractive color model, which involves mixing pigments, inks, or dyes. This model relies on materials absorbing, or “subtracting,” certain wavelengths of light and reflecting the rest. The subtractive primary colors used in modern printing are cyan, magenta, and yellow (CMY). To create a hue that looks like violet, artists and printers typically mix pigments that reflect both blue and red light, while absorbing green and yellow light.
In the CMYK system, a purple or violet-like shade is achieved by combining magenta and cyan pigments. Magenta absorbs green light, and cyan absorbs red light, leaving blue and a small amount of red to be reflected to the eye. This resulting mixture is technically a shade of purple, but it is often called violet in common usage because it strongly resembles the spectral color. The ability for two different light compositions—a single wavelength of violet light and a mixture of red and blue light—to appear visually identical is known as metamerism. This phenomenon explains why a screen or a painting can display a color accepted as “violet,” even though it is physically composed of multiple wavelengths.