Grey and blue are both colors that exist on the visible spectrum of light. However, they are created through different combinations of wavelengths. Grey is an achromatic color, meaning it lacks a specific hue and has zero saturation. It varies between black and white, depending on how much light is absorbed or reflected. Blue, on the other hand, is a chromatic color that occupies a range of wavelengths shorter than green and longer than violet. So while blue is a spectral color with its own wavelength, grey is not directly composed of blue.
The Color Spectrum
The colors we see are determined by the wavelengths of visible light. When all wavelengths of light are combined, we perceive this as white light. As certain wavelengths are subtracted or dimmed, we see other colors. The visible spectrum ranges from violet with the shortest wavelengths to red with the longest. In between we see the colors indigo, blue, green, yellow, and orange.
| Color | Wavelength Range |
|---|---|
| Violet | 380-450 nm |
| Blue | 450-495 nm |
| Green | 495-570 nm |
| Yellow | 570-590 nm |
| Orange | 590-620 nm |
| Red | 620-750 nm |
Blue light has wavelengths ranging roughly from 450-495 nanometers. When we see the color blue, it means those light waves are being reflected while others are absorbed.
Achromatic vs Chromatic Colors
Chromatic colors like blue have specific wavelengths along the visible spectrum. Achromatic colors, on the other hand, have no particular wavelength. They include black, white, and all shades of grey in between.
Grey is considered an achromatic, neutral color as it lacks hue and has zero saturation. Saturation refers to the intensity and purity of a color. Fully saturated colors contain only one wavelength of light. Desaturating a color means removing purity and adding greyness.
Since grey contains no hue, it cannot be composed of blue or any other chromatic color. Instead, grey exists when black and white are combined in varying ratios of shade and tint.
Mixing Pigments vs Light
When working with physical pigments, it is possible to mix blue with other colors to create a greyish tone. This is additive color mixing, meaning the pigments combine to reflect a wider range of wavelengths. The more colors that are mixed, the closer the result gets to neutral grey.
However, optical light mixing works differently. Grey contains an even balance of all visible wavelengths with none dominating. The absorption or reflection of selected wavelengths is what gives blue its chromatic identity. A blue object only reflects blue light while absorbing all other wavelengths. No matter how much blue pigment is used, it cannot recreate the neutral balance involved in grey.
Black, White, and Greys
Going back to the basics, grey by definition is intermediate between black and white. Black objects absorb almost all visible light wavelengths, reflecting very little back to our eyes. White objects reflect nearly all wavelengths evenly in the visible range, showing the full spectrum.
Greys reflect some wavelengths and absorb others in varying degrees between these two extremes. Adding white to black lightens the shade, while adding black to white creates a darker tint. When the balance reaches near equal parts black and white, we perceive this as neutral grey with no hue or saturation.
Tint vs Shade
Within the range of greys, there are subtle differences between tints and shades. A tint refers to grey mixed with white, making it lighter. Common examples are lavender grey and sage grey. A shade refers to grey mixed with black for darker greys like charcoal and gunmetal.
Tinting grey towards white takes it farther from having any saturation or dominant wavelengths, maintaining its neutrality. The same applies to shading grey towards black. So a balanced grey without chromatic influence stays achromatic regardless of lightness or darkness.
Chromatic Greys
While pure grey contains no hue, there are ways to simulate grey by de-saturating a chromatic color. Mixing blue with its complementary color orange can result in a blue-leaning neutral grey. This may absorb more blue wavelengths than a pure grey would.
Using blue as a base for greys makes the end result appear slightly cooler in tone due to the higher levels of blue reflection. But the blue gets muted by adding in its complement. This keeps the grey from becoming too saturated or chromatic.
Blue Hues with Greying
Certain hues of blue inherently contain some greyness due to having less saturation. These include blue with a touch of black added or pale icy blues close to white on the tint scale. Colors like navy, slate, and powder blue lean towards grey, though still maintain a blue chromatic identity.
Between azure, cobalt, ultramarine, and various other blues, greyness can emerge when saturation fades. But these colors retain enough hue to remain in the blue family. They are not actually composed of pure grey, just blue hues desaturated towards greyishness.
The Trick of Lighting
The way light hits an object can also influence perceptions of its color, creating optical illusions. A brightly lit blue may appear more saturated. But seen in dimmer lighting or shadow, the same blue may take on a greyer neutrality.
This optical effect lets blue objects mimic grey in various lighting conditions. But blue remains blue based on its spectral properties, even when illumination tricks the eye into picking up greyness. Only the ratios of reflected to absorbed wavelengths determine the actual color.
Advanced Color Mixing
Modern color technology allows greys to be created more precisely based on specific wavelengths and ratios. Digital RGB color models can mix red, green, and blue light. The equal presence of all three makes white, while their absence makes black.
By selectively adjusting these color components, a vast range of neutral greys can be formed without chromatic influence. This advanced approach confirms grey exists outside the domains of individual hues like blue. It arises from controlled mixing to strike the perfect achromatic balance.
Conclusion
While blue and grey may sometimes look similar under varied conditions, grey is fundamentally undefined by any single color wavelength. The neutrality of grey comes from an even balance of all visible wavelengths or controlled combinations of black and white. Blue only reflects blue while grey reflects the full spectrum evenly. So through the physics of light and color perception, we can confirm that grey is not actually composed of blue.
