What Colour is Water?

Written by Kyla Adams


Posted on December 22 2023


Water is a ubiquitous and essential substance that covers about 71% of the Earth's surface, playing a vital role in sustaining life. While we commonly associate water with its transparent and colourless nature, the question of what colour water truly is may seem perplexing at first glance. In this exploration, we delve into the science behind water's apparent lack of colour and the fascinating interplay of light and molecules that make it so.


The Colourless Wonder:


Water, in its purest form, is indeed colourless. Unlike substances that absorb and reflect light in a way that produces colour, water molecules are exceptional in their ability to transmit light without altering its colour. This transparency allows us to see through water, revealing the submerged world beneath its surface.


The Absence of Pigments:


The colour of most substances is determined by the presence of pigments that selectively absorb and reflect certain wavelengths of light. For example, chlorophyll in plants absorbs light in the red and blue regions of the spectrum, giving leaves their green colour. In contrast, water lacks such pigments. Its molecular structure, consisting of two hydrogen atoms and one oxygen atom (H2O), does not possess the necessary components to absorb or emit visible light in a way that would give water a distinct colour.


The Influence of Impurities:


While pure water is indeed colourless, its appearance can be influenced by impurities and suspended particles. Natural bodies of water, such as rivers, lakes, and oceans, often contain dissolved minerals, algae, and organic matter that can impart a slight colouration. For instance, a high concentration of algae may give water a greenish tint, while dissolved organic materials can cause a yellowish hue. However, these variations in coulor are not inherent to water itself but rather a result of the substances it carries.


The Blue Mystery:


One might wonder why the oceans appear blue if water is truly colorless. The answer lies in the absorption and scattering of light. When sunlight penetrates the ocean, water molecules absorb longer-wavelength red and orange light more strongly than shorter-wavelength blue and violet light. The scattered blue light is what our eyes perceive, giving the ocean its characteristic blue color. The depth of the water and the angle of the sun also contribute to variations in color, with deeper waters appearing darker blue.




In conclusion, the colour of water, or rather its lack thereof, is a testament to the simplicity and elegance of its molecular structure. While pure water is truly colourless, the presence of impurities and the interaction of light with its molecules can result in a spectrum of hues. Understanding the science behind water's apparent colourlessness enhances our appreciation for this essential and life-sustaining substance. Water's ability to refract and scatter light not only contributes to its aesthetic beauty but also plays a crucial role in shaping the visual tapestry of our planet.