In reality there are no coloured objects, either natural or painted. All colours are brain interpretations of energy signals received by them. Such “seen”colours result from the electrical energy pulses passing between the retinas of our eyes and the three rear lobes of our brain, particularly the regions of our brain known as the thalamus and primary visual cortex. Such signals are tiny transfers of energy and all of a two way nature. The received signals are processed and acted upon to deliver the energy display that we see as colour.
Eye movements, both voluntary and involuntary, memories, visual images and spatial awareness all result from energy signals rapidly moving along nerve pathways in our brain. When the visual signals are at a minimum we see a restful blackness.
A major source of these brain signal is the retinal cells in our eyes. They react to the energy levels of the photons of light received by them and therefore to their frequency and wavelength. In response to the received energies our retinal cells send electric energy not continuously, but as pulses along the optic nerve to the thalamus and primary visual cortex. Somehow the energy signals are not communicated as our eyes move from one point of focus to another.
We don’t just “see” coloured images. We also experience them when we dream and when we have unwanted brain nerve cell energy flows as with migraine or concussion. The thalamus is considered a major role player in sleep and wakefulness. It also acts as a nerve cell gateway both passing into storage and getting from storage memory fragments. These are thought to be held in the many synapses that each of the billions of nerve cells in the brain and in the central nervous system have. It would seem that the brain can assemble images from such energy fragments and may explain why our dreams can be colourful and vivid but also creations of what we call in a conscious state imagination.
When retiring to bed and closing my eyes I often see faint colours. They may be reds, blues, purples, etc and are a sign that my brain is still active. When these colours subside and are replaced by black I know I am in a more restful state.
Science describes red, green and blue as being primary colours. It does so because when photons from light emitting sources that are “seen” separately as red, green and blue come to our eyes in equal parts we see white. It means that magenta, a mix of red and blue lights, when mixed with green light make for white. So does yellow light when mixed with blue and cyan when mixed with red light. Understandably such light mixing is described as additive . Added light seen in our brains is always brighter than its separate components.
Retinal cells are of two types called rods and cones. About 120 million rod shaped cells are present in an eye. They are mostly located around the boundary of the retina and are particularly useful at night when lower photon energy numbers are received. Cone cells number about 5 million and are mostly located near the retina’s centre.
There are three types of retinal cone cell. Each has a different energy structure and therefore each responds in its own way to a range of photon energies. Because all we humans have similar but different structures, colour perception isn’t exactly the same for any of us. For a few, like those who have some degree of colour blindness or blindness it is substantially different.
Retinal cone response curve diagrams most often colour the curves red, green and blue as shown. Many descriptions describe the cones as responding to red, green and blue. They are wrong to do so because each cone responds to a range of colours, not to a specific colour and their peak sensitivities are in some cases not aligned with the visible spectrum colour assigned them. It is far better to regard the cones as responding to a range of short, medium and long wavelengths in the visible spectrum. Retinal cone cells respond to photon energies and not to colour.
Contrary to the above view of primary light colours as red, blue and green you were probably taught in art that red, blue and yellow are the primary colours.
When a pair of them are mixed in equal proportions they deliver the secondary colours of purple, green and orange. Our colour wheel illustrates this but also shows marked with a T colours created by mixing primary colours in the proportions of 2 to 1.
Our sun emits a wide range of photon energies including all of those in the visible light spectrum which when added together deliver what our brain sees as white light. We on earth see the sun image as yellowish or even red. That is because some of its emitted visible energies are lost to our atmosphere. To astronauts in space the sun image is white.
The sun’s photon energies that land on earthly objects are absorbed by their atomic particle structures and processed by them. Those objects are all the while releasing most of that photon energy. If they didn’t they would get very hot. The energies released are most often in some changed form and vary according to the object particle energy structure. Some structures emit a full range of visible photon energies and are seen as white, some emit no or few visible photon energies and are seen as black whilst some emit photon energies that our eyes see as a colour.
It is as if the structure has subtracted from the sun light some of its visible light photon energies and reflected the colour we see. In reality the energy structures have processed the received energies and released them at different energy levels, some in the visible light range, some in the non visible photon energies. A black object like iron is releasing most of its energies in the infra red range and its structure is such that it can release such energies rapidly to contacting objects. Our skin touch sensors respond to such energies which is why iron feels very hot in the sun. The total energies gained by structures are never the same as the total energies released by them which is why structures warm up, cool down, expand and contract.
Paint mixed from pigments and applied to an object changes the atomic particle surface structure of that object. By selecting the pigments we apply to an object we can change the range of visible photon energies emitted by the object when a full range of visible light energies fall on it. This way we see the colour of our choosing. The more pigments we mix the duller the released and perceived colour is. We describe the process as subtractive.
Paints are mixtures, not chemical compounds, which means they are composed of tiny, separated and different pigment structures. Each pigment “subtracts” some of the incoming visible light. Each pigment structure has a desire to seek out and draw to it from the incoming photon energies those that are useful and desired by it.
The role of electrons in structures is to seek out and collect energies that are of benefit to other particles in their structure and to avoid or collect and release the energies that are not wanted. The particles in most solid structures have restricted movements and their electrons have little choice but to absorb and subsequently emit energies that are not so much wanted. The more mobile particles in liquid and gas structures can better use their internal energies to avoid the energies they don’t want. The visible energies we see are those emitted by a structure.
Those of you who have printers will probably know that print cartridges are usually of cyan, magenta and yellow. Some articles will tell you that these three colours are more appropriate primary colours. When applied to paper or other structures these cartridge colours are the colours our brain sees in daylight.
We see cyan because its structure is drawing in and using light wavelengths that we would see as red, we see yellow because its structure similarly acts on and uses blue light wavelengths and we see magenta because its structure has a desire for and uses green wavelengths.
If we mix cyan, magenta and yellow together in equal parts the cyan structure draws in and uses red, the magenta and yellow structures do likewise with green and blue related photon wavelengths. No red, green or blue light is released and so we see black because all three primary colours in the daylight are made use of by the mixed structures. It would be very wasteful to mix the cyan, magenta and yellow cartridges to make a commonly used black so most printers have ready mixed black cartridges.
The arguments about which colour primary system is right are a little misleading. Whilst red, green and blue are perhaps an optimal 3 colour primary system for delivering colours in light adding systems like those in television, phones and cameras, it is by no means the only one. In no way can those three colours alone produce all of the colours the human brain can see.
Similarly the cyan, magenta, yellow primary system that subtracts red, green and blue from the light falling on them may be an optimal system for material colouring but it is not the only one and again cannot replicate all the colours our brains can perceive.
It is the case that all primary colouring systems approximate and simplify perceived colours. Additive systems as in televisions, etc have difficulty replicating deep greens, deep blues and violets. We must also understand that the colours of the visible part of the electro magnetic spectrum are just a tiny fraction of the colours that our brain can conjour up. There are millions of colours that the brain can perceive that are not in the spectrum as for example the main colours that are white, black and magenta.
We do not fully understand the brain processes that see colour and I certainly don’t. What I can say is that they are about energy structures changing in response to energy inputs. Perhaps someone out there can explain what is happening in the brain that causes us to see magenta when staring at green and then looking at white and why it is that a migraine aura will move the position of its “seen” image when we move our eyes behind closed lids.
Essentially from the above realise that colour does not exist anywhere other than in our brains and then get back to enjoying the gift of sight and in particular the colours we see.