Grey and blue are two distinct colors that occupy different parts of the color spectrum. At first glance, it may seem unlikely that grey could appear to have a bluish tone. However, under certain lighting conditions and contexts, grey can in fact take on a bluish tint to our eyes. Understanding how and why this phenomenon occurs requires an examination of the different properties of grey and blue hues.
The Color Properties of Grey
Grey is an achromatic color, meaning it lacks any hue and contains only different mixtures of black and white. On the color wheel, it occupies the neutral area between the warm and cool hues. True grey contains equal parts red, green, and blue light. By adjusting these components, grey can shift toward cool blues or warm beiges.
In print and digital formats, grey is made by mixing equal amounts of the CMYK process colors or RGB screen colors. This creates a neutral middle grey. Lighter tints add more white, while darker shades incorporate more black ink or pixels.
The Color Properties of Blue
Blue is a chromatic cool hue located between green and violet on the color wheel. Its place on the light spectrum means it has short wavelengths, which lend it a high amount of energy. Blues contain no traces of warm hues like yellow, orange, or red.
There are a wide variety of different blues. On the color wheel, hues like azure and sky blue lean toward the green side of blue. Navy and indigo contain more violet. All blues derive from combinations of cyan and magenta pigments or light wavelengths.
Why Grey Can Appear Blue
Grey lacks any inherent hue, so how can it take on a blue appearance? There are a few key reasons this can occur:
- Surrounding colors – Grey will pick up color reflections from adjacent hues in a composition through a phenomenon known as simultaneous contrast. Placing grey shapes next to blues causes it to take on a cooler, bluish tone.
- Lighting conditions – The quality of light impacts color perception. Cool, blue-tinged light shining on a grey surface brings out bluish undertones. Warm yellow light makes grey look beige.
- Undertones – Some grey color mixes inherently contain subtle hints of blue or green. Using these shades next to true neutral greys can create a bluer overall effect.
- Optical illusions – Certain patterns like checkerboards can give the illusion of blue alternating squares due to effects on the retina and visual processing in the brain.
When Grey Takes on a Blue Tint
There are many common situations where grey can appear more blue:
- Shadows – Indirect blue skylight bouncing into shaded grey areas results in cooler, bluer shadows on grey objects outside.
- Floors – Grey stone or tile floors can look blue in basement spaces lit with cool fluorescent lights.
- Walls – North facing grey walls with little direct sunlight reflect the blue ambient light in a room.
- Clouds – As water droplets scatter sunlight, clouds turn grey with a bluish quality.
- Winter scenes – The cool clear light of winter can invoke a bluish cast on grey tree bark, rock faces, and snow.
When Grey Reveals Its Blue Undertones
Many mass-produced grey paints, textiles, and products contain small amounts of blue pigments or dyes. Here are some examples of items where blue undertones in the grey shades can become more apparent:
- Jeans – Indigo dyes create a blue foundation in grey denim.
- Cars – Titanium white and blue pearlescent add coolness to grey auto paint.
- Greige paint – Greige mixes grey and beige, but some shades add green and blue.
- Asphalt – Blue slate aggregates create blue-grey asphalt roads.
- Photography – Adding a blue tint modifier makes grey backgrounds feel even cooler.
Using Adjacent Blues
Placing grey shapes, lines or fields next to blue hues causes simultaneous contrast effects that bring out grey’s hidden blue tones. Some examples include:
- Squares – A checkerboard with alternating blue and grey squares will make the greys look bluer.
- Borders – Using blue frames around grey photographs emphasizes blue reflections in the grey.
- Backgrounds – Product shots on blue backgrounds make the grey product take on a blue cast.
- Mixtures – Scattering blue confetti on grey sidewalks causes the ground to look blue-grey.
- Overlays – Translucent blue overlays on a black and white photo give grey tones a cool, bluish quality.
Using Cool, Blue Lighting
The color temperature of light sources directly impacts how our eyes perceive colors. Blue light brings out grey’s hidden cool undertones. Here are some tips for using lighting:
- Outdoors – Photograph grey subjects in the open shade on an overcast day to achieve a blue color cast.
- Indoors – Use blue neon or LED lighting on grey objects to make them take on blue overtones.
- Backlighting – Position blue backlights behind grey subjects for a pronounced blue rim light effect.
- Fill lighting – Adding blue fill lighting to shadow areas creates an overall cooler look to grey elements.
- Special effects – Use a blue spotlight on a dancing grey costume to give it a temporarily blue tint.
Mixing Blue-Tinted Greys
For painting, design, photography and video work, you can mix up custom grey colors with hints of blue yourself. Try these techniques:
- Cyan and black – Add increasing amounts of cyan printer ink or paint to black to make blue-grey.
- Blue wash – Thin down a blue watercolor with lots of water and layer lightly over grey paint for a cooler effect.
- Tint in software – Go into color balance or photo filters and add a touch of blue tint to grey images.
- Blue metering – For film, meter grey cards as if they were a stop darker to intentionally underexpose greys and add blue.
- Color gels – Use lightweight blue theatrical gels to tweak spotlights and modify grey surfaces with blue tones.
Examples in the Natural World
Grey’s chameleon-like ability to take on the colors around it works to the advantage of many animals and organisms. Here are some examples from the natural world where grey takes on blue hues:
- Whales – Blue water reflects onto grey beluga and blue whales, helping them blend into the sea.
- Reptiles – The grey skin of blue-tongued skinks takes on the color of blue ground cover and foliage.
- Birds – In shadow, grey juncos and mourning doves reveal bluish feathers.
- Insects – Grey houseflies have a dusty blue appearance from their transparent blue-black wings overlapping.
- Fish – Fast-swimming blue sharks appear grey-blue when glimpsed underwater.
Grey is adept at taking on the color nuances of surrounding hues and lighting environments. With the right adjacent colors, cool light sources, built-in undertones, optical illusions, and custom mixes, grey can readily take on a bluish tint. Learning to control these conditions gives visual artists and designers powerful tools for making neutral grey come to life with hints of blue.