Color Theory

There is a new bug in town, and it's white. Really white...

A beetle with scales as pale as a ghost could help engineers come up with super-thin, paper-white paints, new research shows.

In recent years, many scientists have looked to nature for new engineering designs, developing such materials as adhesives based on geckos' foot pads and easy-clean fibers inspired by tiny bumps on lotus leaves.

Vukusic decided to focus on color-manipulation and color-flow structures that nature developed, "since it surely must have come up with some really good ideas. We know structural color in butterflies dates back at least 50 million years," he told LiveScience.

Most color in animals often comes from pigments, which absorb specific wavelengths of light and reflect others.

Other colors in animals come from minute structures they possess that make incoming wavelengths of light interact with each other, causing some to emerge weakened and others strengthened.

Familiar examples of structural color are seen with soap bubbles and peacock feathers.

Vukusic explored nature for a structure that generated the color white since it is relatively uncommon in animals. The colors that creatures adopt often help protect them by serving as camouflage.

"White backgrounds are not generally found in, say, savannahs," Vukusic said.

A simple Internet search helped Vukusic arrive at the Cyphochilus beetle.

"The brilliant white of the beetle was just striking to me," he recalled. "I know images can be doctored, but it seemed as if this could be very special. So I just ordered a few for $1.50 each."

He noted that the beetle's whiteness might have evolved to help it blend in with local white fungi.

Beetle-scale balance

In order to appear white, a substance has to scatter all colors of light randomly at the same time. Using electron microscopes, Vukusic and his colleagues found that the scales of the Cyphochilus beetle possess structures made of randomly oriented filaments.

The beetle's scales carefully balance the size of the filaments and spaces between them. This means these structures scatter light far more efficiently than, say, a milk tooth from collaborator Benny Hallam's son, enabling the scales to generate a brilliant white even when very thin — in this case, five millionths of a meter.

Future research could help devise extraordinarily bright white synthetic materials. These could, for instance, help reflect light, replacing the bulky glass mirrors at times found in flat-panel displays, Vukusic said.
This question about the nature of color has got to be one of the trippiest, most counter-intuitive things I have ever encountered. The first time I came across the idea that the color of an object was somehow just a property of its surface texture in high school physics I tried to wrap my head around it, and I just pondered the whole thing until I got a headache. I have tried to avoid thinking about it since then, but when I do encounter the idea it really makes me appreciate the mystery of the mundane things around us. Here is a little more in-depth look at it:

Color of objects

Setting aside illuminant adaptation and contextual effects, surfaces appear to have the color of the light leaving them in the direction of the eye. Since the composition of this light may depend on the orientation of the surface and lighting conditions, the perceived color of an object also depends on these factors. However, some generalizations can be drawn.

Light arriving at an opaque surface is either reflected "specularly" (that is, in the manner of a mirror), scattered (that is, reflected with diffuse scattering), or absorbed – or some combination of these.

Opaque objects that do not reflect specularly (which tend to have rough surfaces) have their color determined by which wavelengths of light they scatter more and which they scatter less (with the light that is not scattered being absorbed). If objects scatter all wavelengths, they appear white. If they absorb all wavelengths, they appear black.

Opaque objects that specularly reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences. An object that reflects some fraction of impinging light and absorbs the rest may look black but also be faintly reflective; examples are black objects coated with layers of enamel or lacquer.

Objects that transmit light are either translucent (scattering the transmitted light) or transparent (not scattering the transmitted light). If they also absorb (or reflect) light of varying wavelengths differentially, they appear tinted with a color determined by the nature of that absorption (or that reflectance).

Objects may emit light that they generate themselves, rather than merely reflecting or transmitting light. They may do so because of their elevated temperature (they are then said to be incandescent), as a result of certain chemical reactions (a phenomenon called chemoluminescence), or for other reasons (see the articles Phosphorescence and List of light sources).

Objects may absorb light and then as a consequence emit light that has different properties. They are then called fluorescent (if light is emitted only while light is absorbed) or phosphorescent (if light is emitted even after light ceases to be absorbed; this term is also sometimes loosely applied to light emitted due to chemical reactions).

To summarize, the color of an object is a complex result of its surface properties, its transmission properties, and its emission properties, all of which factors contribute to the mix of wavelengths in the light leaving the surface of the object. The perceived color is then further conditioned by the nature of the ambient illumination, and by the color properties of other objects nearby (see the article Color constancy); and finally, by the permanent and transient characteristics of the perceiving eye and brain.

... now contrast that with "structural color" which is the deal with the white beetle:

Structural color

Structural colors are colors which are caused by interference effects rather than pigment. Colors are produced when a material is scored with fine parallel lines, formed of one or more thin parallel layers, or otherwise composed of microstructures on the scale of the color's wavelength. If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colors: the blue of the sky, aerogel of opals, and the blue of human irises. If the microstructures are aligned in arrays, for example the array of pits in a CD, they behave as a diffraction grating, the grating reflects different wavelengths in different directions due to interference phenomena, separating white light into colors. If the structure is one or more thin layers then it will reflect some wavelengths and transmit others, depending on the thickness of the layer(s).

Structural color is responsible for the blues and greens of many bird feathers (example, blue jay feathers) as well as certain butterfly wings and beetle shells. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle.

Structural color is studied in the field of thin-film optics. A layman's term that describes particularly the most ordered structural colors is iridescence.

aren't colors amazing!!!
I am going to have a hard time thinking about anything else today!
(I guess theoretically this could have some pretty interesting ramifications for race and identity too, based on whether one's skin color is "structural color" or "pigment..." and maybe can help diffuse the tension from a situation like the following (which is purely fictional, and meant only to inspire humor):

Monique: ...so what did you do for the holidays, Heather?
Heather: I went home and did the whole Christmas thing with my family - I got 2 sweaters from J. Crew, a new pair of jeans from Abercrombie, and a bunch of other stuff... how about you - did you celebrate Kwanzaa?
Monique: Kwanzaa!? Damn, Heather, why do you always have to act so white?
Heather: (quizzical look) ...well at least I'm not as white as the Cyphochilus beetle...
Monique: well, I guess that's true... I mean it's not like your skin color is structural or anything... ha! well I'm sorry... I guess we can still be friends.