Light is made up of different wavelengths that our eyes perceive as different colors. When different colored lights are mixed together, the resulting color we see depends on the specific wavelengths being combined. Green light has wavelengths of 495-570 nanometers, while blue light is in the range of 435-495 nm. Mixing these two colors of light results in a new color that our eyes and brain interpret based on how the wavelengths stimulate the color-sensitive cones in our retinas.
How Light and Color Work
In order to understand what color results from mixing green and blue light, it’s helpful to first review some basics about light and color.
Visible light from the sun or light bulbs contains a spectrum of wavelengths ranging from about 400-700 nm. The different wavelengths stimulate the three types of color-sensitive cone cells in our eyes in different amounts. Red cones are most sensitive to long wavelengths, green cones respond most strongly to medium wavelengths, and blue cones are stimulated primarily by short wavelengths.
Our visual system and brain process the information from the three cone types to give us the perception of different colors. When all wavelengths of visible light are present in relatively equal amounts, we see white or gray. When only a small band of wavelengths strike our eyes, we see saturated colors like red, green, or blue. Mixing wavelengths together in different ratios produces all the variety of colors we can perceive.
Mixing Green and Blue Light
When we mix light of two different wavelengths, such as green and blue, the cone cells respond to the combined stimulation. Green light strongly activates both the green and red cones. Blue light stimulates the blue cones predominantly.
When green and blue light mix, the red and green cones are stimulated strongly, while the blue cones receive moderate stimulation. This combination of cone cell signals produces the perception of cyan – a bluish-green color.
The exact shade of cyan will depend on the relative intensities of the green and blue light that are mixed. Equal intensities will produce a cyan halfway between blue and green. Increasing the intensity of either the green or blue source will shift the color toward that component color.
Color Addition and Subtraction
The mixing of light colors is known as color addition, because the wavelengths are being added together. This is different from mixing pigments like paints, dyes or inks, which absorbs certain wavelengths. Mixing paints results in color subtraction, because some wavelengths are being removed by each pigment.
For light, combining different colors generally results in a lighter or brighter color. Mixing green and blue light together produces the lighter cyan color mentioned previously. Adding red light as well results in white light, since all the cone cells are being strongly stimulated.
In contrast, mixing paints yields progressively darker colors as more pigments absorb light. Combining green, blue and red paint produces black, the absence of light reflection.
The Color Wheel
| Color | Wavelength range (nm) |
|---|---|
| Red | 620-750 |
| Orange | 590-620 |
| Yellow | 570-590 |
| Green | 495-570 |
| Blue | 450-495 |
| Violet | 380-450 |
The relationship between different colors of light can be visualized using a color wheel. The visible spectrum of light is arranged in a circular format, with each color blending into the next. Colors opposite each other on the wheel are complementary colors.
Mixing complementary colors produces a white light, since together they contain a full spectrum of wavelengths. Green and magenta are complements, so combining green and magenta light would also result in white.
Colors next to each other on the color wheel, like green and blue, tend to produce pleasant blended hues when mixed. These neighbors are known as analogous colors. Analogous color combinations, like cyan made from blue and green, are commonly used in art, design, and photography.
Cyan in Nature
While cyan itself is not found in the pure spectral colors of the rainbow, it is a common color produced by the mixing of green and blue wavelengths in nature.
Many bird species show cyan colors in their plumage. The structurally-produced color comes from the scattering of light off finely structured feather barbs. Shorter blue wavelengths reflect off the outer portions, while longer green wavelengths bounce off the inner layers.
Cyan also appears commonly in insects and reptiles. The morpho butterfly has shimmering blue wings that use optical interference effects to reflect predominantly blue and green wavelengths. Damselfly wings also produce a cyan color through similar nanostructure mechanisms.
Among reptiles, the green tree python has chain-like scale patterns that differentially reflect blue and green light to give regions of cyan coloration. Cyan color can provide camouflage or serve as a signal to other members of the species.
Cyan in Technology
Cyan has been an important color for color printing and display technologies. In the late 1800s, a cyan photographic dye was one of the first stable color agents used in early color photography experiments.
Later on, cyan became one of the primary colors used for color printing and displays along with magenta and yellow. Mixing cyan, magenta and yellow at full intensity theoretically produces the same result as mixing red, green and blue light.
On computer displays and televisions, cyan is created by exciting the green and blue color channels together. Digital image files and graphics tools like Photoshop use the RGB color model, with cyan being a mix of full green and full blue values.
Cyan is also used in color inkjet and laser printing. The CMYK (cyan, magenta, yellow, black) color model is used, with the cyan ink corresponding to the green region of the color spectrum. Along with magenta and yellow inks, a full range of colors can be produced on paper.
Curiosities About Cyan
Here are some additional interesting facts about the cyan color produced by mixing green and blue light:
– Cyan is sometimes referred to as aqua or electric blue.
– In color psychology, cyan is associated with calmness, tranquility, and refreshing coolness. It evokes water and clear blue skies.
– Cyan on a black background provides extremely high contrast, which is why early computer monitors used green text on black screens.
– Cyan is the complementary color to red. Painters may add small amounts of cyan to tone down the intensity of reds.
– In the well-known RYB color model, cyan is considered a primary color instead of blue. The RYB primaries are red, yellow, and blue (which contains cyan).
– There is a rare type of color blindness called tritanopia where people cannot perceive blue and yellow. To them, a mix of green and blue would look white.
– Cyan is one of the colors used in four-color CMYK printing. The other two are magenta (mix of red and blue) and yellow (green and red mix).
– In web design, cyan combined with black is recommended for text to provide extremely high contrast for improved readability.
Conclusion
When green and blue light mix together, the combination of wavelengths produces the color we see as cyan. This bluish-green hue results from the combined stimulation of the red/green and blue color receptors in the eye. Cyan can be considered an “additive” color, formed by the aggregation of different wavelengths.
The exact shade of cyan depends on the relative amounts of green and blue light – increasing one component shifts the color towards green or blue. Cyan is an example of an analogous color combination that is found pleasing and abundant in nature. It also has importance in color printing, photography, and digital media. Exploring the interactions between different wavelengths of light reveals the fundamentals of how we perceive color.
