An infrared camera helps a human "see" infrared colors by converting the infrared colors to red or green. An infrared camera, therefore, does not really allow you to see infrared colors. It allows you to see red colors that are in the same spatial pattern as the infrared colors.
An intelligent alien on a distant planet that has never had sight can still measure the color red using tools in a similar way to how humans measure infrared colors without being able to see them.
Physically, there are two kinds of colors: pure spectral colors and mixed colors. A pure spectral color consists of a beam of light that is a simple sine wave with a single wavelength.
The wavelength of the light is the color of the light. Light is a waving of the electromagnetic field. The distance in space between the peaks of an electromagnetic wave is its wavelength, and hence its color. When you run a narrow beam of white light through a glass prism, it spreads the light out into its spectral colors.
The resulting red, orange, yellow, green, blue, and violet pattern and all the colors in between shows the span of possible visible spectral colors.
Red has a relatively long wavelength compared to the other visible colors. On the other end of the visible spectrum, violet has a relatively short wavelength. All of the visible colors have wavelengths that are on the scale of hundreds of nanometers or tenths of microns. A mixed color is a combination of spectral colors. Exactly how much of each spectral color is added to the mix determines what the final color is. As before, the exact nature of a mixed color is a physical property that exists independent of humans.
How a mixed color is perceived is human-dependent. When light shines on an object some colors bounce off the object and others are absorbed by it. Our eyes only see the colors that are bounced off or reflected.
This mixture is known as white light. When white light strikes a white crayon or marker barrel, it appears white to us because it absorbs no color and reflects all color equally.
A black crayon or marker cap absorbs all colors equally and reflects none, so it looks black to us. While artists consider black a color, scientists do not because black is the absence of all color.
All light rays contain color. This may have hastened his death, but the real cause was bowel cancer and a perforated ulcer.
The only colour in the English language that takes its name from a fruit is orange. It all goes back to China around 4, years ago when oranges were first cultivated and travelled west down the Silk Road. They went to Northwest India where the Sanskrit word for an orange tree — narrangah — served as the root for many languages as oranges were planted and sold — Narang in Farsi, naranj in Arabic and naranja in Spanish.
The English word orange is a corruption of the Sanskrit. Before the fruit arrived, the English word for the colour was geoluread yellow-red but in the 16th Century orange took over. In some languages, however, the two are separated. In Afrikaans, for example, the colour is oranje but the fruit is lemoen and several languages, including Himba, Nafana and Piraha, have no word for the colour.
The first colour to come in synthetic form was purple. In , William Henry Perkin, an year-old chemistry student, was told to conduct an experiment using coal tar to find a cure for malaria. He failed but was intrigued with what happened when he dipped a piece of cloth into his mixture of coal analine and chromic acid: it came out purple and held its colour.
He patented the dye he called mauveine and became a rich man after it was mass-produced. It had a revival in the late s as the colour of the counter-culture and is now seen as a feminine alternative to pink.
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