I have always been interested in various aspects of colour. What is it? What's its purpose in nature? How are we affected by it? And so forth. The topic includes everything from science to art. My readers here may already have seen examples of this interest; my series about purple comes to mind, but there are numerous examples of other texts, other topics, where aspects of colour often turn up: eyes, vision, art, gems, symbols, even medicine.
This is the first article in a short series, where colour plays the main role.
The Nature of Colour
Colour is not a quality of the object as such. The sensation of colour is due to certain processes in the cortex of the brain, and a result of light reaching our retina (in the eye), from where a nervous impulse passes through the optic nerve to the cortex. Which colour we "see" depends on the wavelength of the light reaching our retina. So, the experience of colour is something happening in our brain, a representation of a certain nervous stimulation.
Look at a rainbow. It clearly shows how "white" light can be divided into red, orange, yellow, green, blue, indigo and violet. They are all part of a spectrum, and each one consists of light in certain wavelengths. When an object is exposed to light, some of the wavelengths (colours) are absorbed while the rest are reflected. The reflected ones are those our retina is catching, and they determine the colour we "see".
When light of all wavelengths is absorbed, we see black. When light of all wavelengths is reflected, we see white. Black, white and grey are called "achromatic" colours. All others are "chromatic".
Wavelengths are often expressed in a unit called Ångström (symbol Å). One Å is one hundred-millionth of a centimetre. It is named after Swedish physicist Anders Jonas Ångström (1814-1874).
Then we approximately get this:
Red 8000-6000 Å
Yellow 6000-5800 Å
Green 5800-5000 Å
Blue 5000-4300 Å
Violet 4300-3900 Å
The spectrum contains waves longer than 8000 Å and shorter than 3900 Å as well, but they give us no sensation of colour, although they do affect our cells.
The ones over 8000 Å, infra-red, are perceived as warmth. The ones shorter than 3900 Å, ultraviolet, affect our cells chemically.
A small number of totally blind people have demonstrated an ability to feel colours with their fingertips. They describe it as a sensation of shift in temperature. Given that we all feel noticeable and very real warmth from infra-red light, it is not very far-fetched to think that their claimed ability is perfectly real and possible... with practice!
An interesting detail to note is that colours are often experienced and described as warm or cold. Red (long waves) is the warmest; violet-blue (short waves) is the coldest. The intuitive connection between colour and temperature goes very deep.
Warm colours are: red, orange, yellow, and some greens. Cold are: violet, blue, turquoise, and some greens. The achromatic colours black, white, and grey are considered as neutral, which is not entirely correct. Let's say theoretically they are, but never in practice. If you have ever worked with colour artistically, you know that black always has a touch of either blue or brown - one cold, the other warm; and white has a touch of either blue or yellow - also a cold and a warm alternative. If you paint with just black, white and greytones, a general rule is that they should all be either warm or cold, not some of this and some of that in the same painting.
The Colour Wheel
Artists, Alchemists, Philosophers and Scientists have always attempted to systematise colours – to create a model expressing how colours are inter-related. The most successful and useful model is probably the colour wheel, which basically shows how colours gradually change into other colours. They are placed in a circle, with complementary colours opposite to one another. Historically, a lot of colour wheels have been created, but there is no reason right now to look at them all in detail. Below we can see a modern colour wheel.
Brownish and Grey-brownish colours do not appear in this wheel. They are generally obtained by mixing not adjoining (main) colours with each other. For instance, if you mix red and yellow, you get orange, a colour you find between red and yellow; but if you mix red and green, you get brown.
To be continued...
(This article in an excerpt from the introduction of my forthcoming e-book, "Chromaticon", a book exploring colour in culture and nature. Parts of it are based on material previously published in Meriondho Leo.)
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I found it interesting, never new that there's this thing called wavelengths in colour. And my favourite colour belongs to cold colours and that was blue. Your article was very educational for me.