This realisation that I often think about always blows my mind, I am studying something that isn’t a physical thing (using the term loosely). The idea of colour is something that is a scientific measurement, it is a wavelength that bounces off an object at a particular frequency to provide the sensation of colour. The fact it is a measurement means it is purely subjective and everyone has their own unique experience. Visible radiation
Indeed, rays properly expressed, are not coloured. There is nothing else in them but a certain power or disposition which so conditions them that they produce in us the sensation of this or that colour. – Sir Isaac Newton, Optiks, 1704
As humans we can only see approximately 380nm – 780nm worth of electromagnetic waves; what we define as ‘the visible light spectrum’. This scientific measurement is how we define light and colour, so a wavelength at 470nm would be considered blue, whilst a wavelength at 600nm would be considered orange. This even comes down to tiniest changes in the wave as a light at 468nm (greenish blue) would appear more greenish than a wave at 483nm.
When you take this approach towards light you begin to encompass how we define it as a CIE colour space model, and how something such as ACES fits into this as it caters for wavelengths beyond the visible light spectrum. Our perception of all of this depends on the sensitivity of our cones to short, medium, and long waves in the band of the wavelength spectrum. Any given colour is decoded by these cones mixing our primaries to form a depiction of the wavelength.
The other way of looking at the visible light spectrum goes beyond scientific measurement and focuses on the emotional impact of witnesses these wavelengths. The sensation of light and colour is something to be felt, it changes your perspective on the world around you as you gain associations as to what colour means (i.e. red on a road sign means danger). It is important emotionally to our lives, the creative viewpoint of colour is never-ending whilst science has managed to define what light actually is.
Yellow can express happiness, and then again, pain. There is flame red, blood red and rose red. There is silver blue, sky blue and thunder blue. Every colour harbours its own soul, delighting or disgusting or stimulating me. – Emil Nolde, 1942
At the end of the day the concept of light and the way each subject perceives it comes down to the eye of the beholder. This is why I feel the use of light and colour has no set rules because everyone views it different and nobody can truly share the same experience. We can define what a colour is in a numerical form, but I may see that as a slightly different tint than the next person. Despite being presented the same image, each person responds different and takes away their own unique experience.