The color violet often conjures up images of the purple flower of the same name. With its rich, deep hue, violet is an eye-catching color that stands out from the crowd. But is violet actually a shade of red? The answer is more complex than you might think.
Violet is a spectral color, meaning it has its own wavelength of light on the visible spectrum. The wavelength for violet light is approximately 380-450 nanometers. This wavelength range sits at the short end of the visible spectrum, next to blue and indigo. In contrast, red has a longer wavelength of approximately 620-750 nanometers at the opposite end of the visible spectrum. So in terms of wavelengths, violet and red are quite far apart.
However, when it comes to how we perceive color, things get more complicated. The way we see color depends on the cones in our eyes that detect different wavelengths of light. There are three types of cones: red cones, green cones, and blue cones. Violet light strongly stimulates the blue cones in our eyes but provides relatively little stimulation of the red and green cones. This pattern of cone stimulation is what creates the perception of violet as a distinct color.
The Visible Spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. The wavelengths of light that comprise the visible spectrum range from approximately 380 nanometers to 750 nanometers. The visible colors from shortest to longest wavelength are:
| Color | Wavelength (nm) |
|---|---|
| Violet | 380-450 |
| Blue | 450-495 |
| Green | 495-570 |
| Yellow | 570-590 |
| Orange | 590-620 |
| Red | 620-750 |
As the table shows, violet and red fall on opposite sides of the visible spectrum, with violet at the short wavelength end and red at the long wavelength end. This separation indicates that they are distinct spectral colors.
Cone Cells and Color Perception
The human eye contains two types of light receptors – rods and cones. The cones are responsible for detecting color. There are three types of cones, each containing pigments that are sensitive to different wavelengths of light:
- S cones – sensitive to short blue wavelengths of light
- M cones – sensitive to medium green wavelengths
- L cones – sensitive to long red wavelengths
When light enters the eye, it stimulates the three different cone types to varying degrees. The specific pattern of stimulation amongst the three cone types creates all the colors we see.
For example, violet light strongly stimulates S cones, weakly stimulates M cones, and barely stimulates L cones. This cone stimulation pattern leads to the perception of violet as a distinct color.
Red light, on the other hand, strongly stimulates L cones, moderately stimulates M cones, and barely stimulates S cones. This creates the perception of red as its own color.
So although violet and red physically occupy opposite ends of the visible spectrum, we perceive them as distinct colors because of how they differentially stimulate the cone cells in our eyes.
The Visible Spectrum is a Continuum
The sequence of colors in the visible spectrum represents a continuum of wavelengths, with no clear dividing lines between one color and the next. Between violet and red, there are gradual transitions through every shade of blue, green, yellow, and orange.
Perceptually, we categorize these wavelengths into distinct color bands like violet, blue, green, etc. But in reality, there are no sharp borders where violet ends and blue starts, for example. It is a seamless progression of gradually changing wavelengths.
So violet blends smoothly into blue, blue into green, and so on, until green ultimately blends into red at the opposite end of the spectrum. All of the colors we see are connected in this continuous gradation. Violet is not an isolated island, but part of a flowing sequence.
Color Mixing and Overlapping Sensitivity
When it comes to mixing light wavelengths, things get even more complex. If you combine different wavelengths of light, the eye perceives a blended color. For example, blue and red light shone together will mix to produce the perception of violet or magenta (depending on the exact wavelengths and proportions).
This is because the wavelengths for violet/magenta stimulate both the S cones (which violet dominates) and the L cones (which red dominates) simultaneously. The brain essentially fuses these signals together into a violet/magenta perception.
In a similar way, even though violet light itself does not stimulate L cones strongly, there is some slight overlap in sensitivity between the S, M and L cones. So violet provides a small amount of stimulation to not just S cones, but also M and even L cones.
This means violet light triggers red and green cones to a limited degree. The brain takes this full pattern of cone stimulation and constructs the sensation of violet as distinct from red. But the subtle influence of L cones means violet is not completely isolated from red either.
Color Vision Deficiencies
When someone is color blind or color deficient, they have an impaired ability to distinguish certain shades. This is usually because they are missing or have defective cone cells.
For example, those with red-green color blindness lack functioning M cones. As a result, they cannot distinguish red and green hues well. Without the full complement of cone cells providing distinct patterns of stimulation, their perception of all colors is altered.
To a person with red-green color blindness, violet may appear more heavily mixed with red than it does to someone with typical vision. This demonstrates how much the perception of violet depends on having properly functioning M cones, in addition to S and L cones. All cone types work together to generate the complex sensation we call violet.
Pigment vs. Light
Another wrinkle is that color seen in pigments and dyes doesn’t necessarily correspond to spectral light. Pigments selectively absorb certain wavelengths of light while reflecting others. The wavelengths that are reflected determine the color we see.
Violet pigment reflects violet light while absorbing other wavelengths. But the molecular composition of violet pigment is not related to the cone stimulation caused by violet light. We just happen to see the same resulting color.
So viewing violet as a color related to red is really only relevant when discussing light wavelengths. With pigments, violet simply reflects violet light selectively.
Cultural and Linguistic Associations
Different cultures and languages categorize colors differently. Just because English speakers define violet as distinct from red does not mean other languages draw the same lines.
Some languages do not distinguish violet from blue. Others have entirely different color words that group what we call violet and red together.
These kinds of linguistic differences provide evidence that color perception is not as hard-wired as we may assume. The way we define colors has a lot to do with cultural naming conventions, not just visual neurobiology. So violet’s status as unrelated to red relies on cultural context too.
Conclusion
While violet has a shorter wavelength of light than red and stimulates different cone cells in the eye, there are many factors that connect violet to red within our complex color vision system. The visible spectrum is a continuum, there is overlap in cone sensitivity, wavelengths can mix to create new colors, and perception depends on having properly functioning cone cells. Plus, linguistic categories influence how colors are grouped and distinguished. For all these reasons, it is an oversimplification to say violet is entirely unrelated to red when it comes to human color vision. The relationship between spectral colors is wonderfully nuanced.
