The question of whether a color can be both reddish and greenish at the same time is an interesting one that has implications for our understanding of color perception. While red and green seem like opposites on the color wheel, there are some shades that appear to blend both hues together. In this article, we will explore the visual science behind reddish-green hues and discuss whether they can truly exist or if it is just an optical illusion.
The Color Wheel
To understand reddish greens, we first need to look at how colors are organized. The color wheel arranges colors into a circle based on their hue. Opposite colors are complementary, meaning they create a striking contrast when placed side-by-side. Red and green are directly across from each other on the wheel, making them complementary colors. Mixing complementary colors together produces a neutral grey or brown.
Color Mixing
When mixing paint colors, adding red makes a color more red and adding green makes it more green. Mixing pure red and pure green paint produces a dark, muddy brown. However, light mixing follows different rules. Combining lights of two colors makes the result brighter and shifts it toward a blended hue between those colors.
Mixing red and green light together produces yellow. The more red light added, the more reddish-orange the resulting yellow becomes. The more green light added, the more lime-like the yellow appears.
Impossible Colors
While lights can blend to create intermediate hues, there are some color combinations that seem impossible. For example, we cannot see a pure reddish-green because the eye’s color receptors cannot be simultaneously excited for both red and green in the same spot. Responding to one color strongly suppresses receptors for the other color.
Opponent Process Theory
The opponent process theory of color vision helps explain this phenomenon. It states that our eyes contain receptors responding to either red OR green, as well as receptors responding to blue OR yellow. There are no receptors tuned specifically to intermediate hues. Information from these receptors is processed further along visual pathways and blended to enable perception of millions of colors.
But at the very initial color-sensitive stage in our retina, red and green are opposed and cannot co-exist. This makes a true reddish-green undetectable.
Color Illusions
While a pure reddish green cannot be seen, there are some color illusions that seem to achieve this effect. For example, looking through a color filter that shifts the visible spectrum can make orange appear more red and yellow appear more green. If these altered colors are placed adjacent to each other, they can produce the sensation of a missing reddish-green.
Impossible Color Demo
| Color 1 | Color 2 | Illusory Color Between |
|---|---|---|
| Orange through red filter | Yellow through green filter | Seems reddish-green |
The optical effect seen here demonstrates that color perception is not just about the wavelength of light entering our eyes. Context and contrast effects in the surround also influence what we see. While a true reddish green remains impossible, this illusion lets us glimpse these phantom colors.
Color Spaces
Looking at how color is represented numerically can shed some light on the reddish-green question. There are different color models or spaces for defining colors based on mixes of primary colors.
RGB Color Space
The RGB color space uses red, green, and blue lights to create colors. Combining RGB components in different ratios produces millions of colors visible on TVs and computer screens. In RGB space, reddish greens can be defined numerically but cannot be displayed properly because RGB monitors use the same red-green opponent channels as our eyes.
CYMK Color Space
The CYMK color space used for printing relies on cyan, yellow, magenta, and black inks. Since these inks do not activate the red-green opponent channels, CYMK can generate reddish-green colors by layering magenta and yellow. However, the result is still not a spectral color matching a single wavelength of light.
Color Theory
In color theory used by artists and designers, definitions of hue, saturation, and brightness provide another way to think about impossible colors. Reddish green can be imagined as a color halfway between red and green in hue, moderately saturated, and medium lightness. Even if this color can’t physically exist, it can be defined abstractly. Designers may utilize these conceptual colors in creative ways even if they remain impossible to reproduce exactly.
Spectral Power Distribution
From the perspective of the physics of light, color is defined by spectral power distribution. This refers to plotting light’s power across different wavelengths in the visible spectrum from 400-700 nanometers. For a color to be considered spectral, it must have a single peak at one wavelength.
There is no single wavelength that could produce a reddish green, so by the standards of spectral power distribution, reddish green is impossible. Only metameric colors created by mixing multiple wavelengths can approximate this mythical hue.
Natural Reddish Greens
Some rare natural phenomena come close to reddish-green hues. Certain minerals can exhibit oxidation states that selectively reflect close to reddish-green. And refracted sunlight passing through moisture in the atmosphere can also separate into unusual color bands. But in both cases, the light reaching our eyes is complex, not a pure spectral color. These effects serve as reminders of how color depends on context and viewing conditions.
Synesthesia
For people with synesthesia, a blending of the senses where numbers, words, or sounds induce color perceptions, reddish green may exist. Synesthetes often report seeing impossible colors not found in the real world in response to certain stimuli. Their experience provides a unique window into reddish green as a cognitive phenomenon that can be imagined but never directly seen.
Mind and Matter
The search for reddish green highlights that color is not just a physical property of light. It requires our visual system to process signals and generate an experience in the mind. No wavelength of light directly looks reddish green. We can define this color mathematically or imagine what it might look like, but our eyes cannot match it to any real stimulus. Perception generates colors that vision science shows remain partly unmixable. In this way, the case of reddish green reveals the complex dance between mind and matter underlying consciousness itself.
Conclusion
While reddish green remains impossible to see as a real spectral color, this semi-imaginary hue reveals fascinating insights about color vision. Our eyes employ opponent channels that make a true fusion of red and green impossible at the receptors. But color perception also involves many layers of neural processing that can produce contextual effects and color constancy. And there are still unexplainable experiences of phantom colors in phenomena like synesthesia. The quest for reddish green demonstrates that there are still mysteries to how mind, matter, and perception create the qualia of our world.
