Light is electromagnetic energy that can pass through transparent objects and empty space without requiring any medium for its transmission from one place to another.
There are different views about colours. Light, in actual effect, is a combination of different frequencies and various wavelengths. Feeling of a particular wavelength, having a typical frequency, by the retina and the mind is known as colour.
In 1666 Sir Isaac Newton expounded the Principles of Gravitation and Theory of Colours. When the sunlight or the light waves, according to this theory, pass through a prism, they disperse according to their frequencies into seven bands and we know this grouping of waves, as colours. All the other colours are shades of these seven bands of colours. This band of rainbow colours resulting from the dispersal of light waves is named as spectrum.
Violet indigo, blue, green, yellow, orange and red, are the colours in a spectrum our eyes are more sensitive for yellow and green colours and interestingly the sunlight also boosts yellow and green more than other colours.
Colours witnessed in a spectrum are only the visible part of the spectrum. The waves, which have wavelengths shorter than violet waves cannot be seen by our eyes e.g. ultra-violet rays, x-rays, gamma rays etc. Similarly the waves of larger wavelengths than the red also cannot be seen e.g. infra-red and microwaves.
It is not so that everybody can witness the colours other than the seven colours of the spectrum, there are people who can witness even the invisible waves of the Electromagnetic Spectrum.
How do we see colour? There are different views in this regard. The idea that is generally accepted is known as Classical Theory.
Classical Theory was presented by renowned Physist Mr. Young and anatonomist Mr. Helm Holtz. This is also called Young Helm Holtz Theory. Both these scientists were moved to see that only three colours are enough to form other compound colours.
Three types of cones, according to this theory are there on the retina. One type of cones is sensitive for the wavelengths of blue colour, other is sensitive for yellow colour and third type of cones is to feel the red. The wavelength of the colour falling upon the retina triggers the concerned cone and thus the particular colour is sighted. All the colours are witnessed because of triggering of two or three cones e.g. wavelength of purple activates the cones sensitive for red and blue. Resulting activation of these two cones we see purple colour.
Why do we see colours? Colour, in actual fact, is that quality of the light which it expresses after mixing with darkness. We see an object black because it absorbs all the waves of the light and we see an object white because it reflects all the waves of the light. We see an object red because it reflects the waves of the red colour only and absorbs all the other waves. And, the same is true for all other colours.
Why are the colours? How do they form? What are the primary colours? Exact situation is yet not clear. Some consider that there are four primary colours; some say these are three. And, according to few, black is the basic and primary colour. The great Spiritual Scientist Qalander Baba Auliya declares: blue is the basic colour.