WHAT IS THE COLOUR OF WATER?
Common people normally sneer at questions of this nature only because their answers emanate from common sense or the apparent reality which the eyes, through its receptors, habitually send to the brain for interpretation. This is such a frankly natural process in cognition that humans generally are bound to rely heavily on sensation to make sense of the universe. However, one might seize upon the conclusion that our sense organs are designed not to comprehend the universe but to aid our survival. If we then argue their usefulness, we can avoid the category error of believing that they aid us in reaching a definitive description of the universe. Why do humans have eyes? To see the world as it appears to them in physical terms. Why do we have two eyes? To help the brain coordinate our sight and place the objects we see within binocular vision. Does the cognitive interaction between the eyes and the brain produce an exact knowledge of the world we see?
To decode a cryptic message on a piece of paper with ultra violet rays is a self-evident means to prove that apparent reality—the tree, the blue sky, the moon etc-- is reality cut in half. We may also bring the same scientific mind to study water not in terms of its properties but in regard to its actual nature. That it would take many years before I eventually realised that water is not colourless is enough proof that I was as ignorant as anyone who dismisses this question on the spot or derives his answer from common sense.
WATER IS CLEAR BUT NOT WITHOUT ITS OWN COLOUR. IT IS CLEAR IN A GLASS CUP(SMALL QUANTITY), BLACK ON THE OCEAN AND BLUE FROM THE ORBIT.
Water is an interesting example of how colour is a product of reflection, refraction and absorbsion of light and Isaac Newton’s experiment proves that light is the source of colour subject to certain conditions. It is therefore important to note that light cannot be dispersed in water in small quantity. Another well-worn example of how limited we are by our sensation is the cloud viewed as fleecy white substance which it is not when properly studied. It is, as a matter of fact, a heavy concentration of raindrops. The sky is black but the atmosphere produces blue light more than any wavelength so that when white light from the sun reaches it we are only able to see a blue sky. Water is clear when light travels unhindered through it. (To experiment it, get a glass of water and allow light to pass through it).
However, the ocean as a vast body of water hinders light as it travels through it and before it reaches the bottom. And so, water is only able to reflect the blue scattering of the atmosphere so that we are intrigued by the blue ocean.
According to Zachary Ingham, our biological senses do not offer anything close to a complete description of the world: they are designed to help us survive and reproduce and not to comprehend the universe. Concordantly, I recognise the brain as the most important asset our species evolved to conquer his environment and comprehend the universe. After all, it was Sigmund Frued who said the true founder of civilisation was the first man to hurl an insult instead of a rock.
Further reading: Plato, Aristotle and Kant on Metaphysics