Colour shapes how we see the world. But what is it, really? Is a red rose actually red? The short answer is no. Colour does not exist as an independent object outside your own brain. It is the result of an interplay between light, matter and millions of years of evolution.
It begins with light
To understand colour, you have to look at its source: light. Visible light is a form of electromagnetic radiation. It occupies the same spectrum as radio waves and X-rays, but falls precisely within the narrow range that the human eye can detect. This visible light consists of different wavelengths. As white sunlight travels through a prism or a raindrop, it refracts and splits into a spectrum of colours: red, orange, yellow, green, blue, indigo and violet.
Pigment
An object has no inherent colour of its own. However, matter possesses the ability to absorb certain wavelengths of light and reflect others. A ripe tomato absorbs almost all wavelengths from the spectrum, except for the red portion. That specific wavelength bounces off, enters your eye and sends a signal to your brain. Pigments, whether derived from nature or manufactured in a factory, determine which wavelengths are absorbed and which are reflected back.
Evolution
Our perception of colour is no coincidence; it is a biological adaptation. Most early mammals were nocturnal and relied on just two types of colour receptors (dichromacy). When the ancestors of modern humans moved into the trees during the day, their lifestyle evolved. A genetic variation emerged that granted primates a third type of colour receptor, making us trichromatic:
- L-cones: sensitive to long wavelengths (red-orange).
- M-cones: sensitive to medium wavelengths (green).
- S-cones: sensitive to short wavelengths (blue).
Why was this adaptation so valuable? Primates that could spot the subtle difference between young, nutritious red leaves and mature green ones, or pick out ripe red fruit hanging in a dense green canopy, had a significantly higher chance of survival. Colour perception thus developed primarily as an effective tool for identifying food.
From biological stimulus to emotion
The moment light passes through the lens and hits the retina, the cones convert light energy into electrical signals. The visual cortex at the back of your brain processes this data into a conscious experience: you see colour. At the same time, specialized light-sensitive cells in the retina (unrelated to conscious vision) specifically detect blue light. This information travels directly to deeper brain structures, such as the hypothalamus and the amygdala, which regulate our hormones, alertness and emotions:
- Red and orange biologically trigger rapid alertness. Our brain associates them with ripe food, fire or blood, immediately capturing our focus.
- Green and natural tones are associated with safe, water-rich and hospitable environments, inducing a calming effect.
- Blue light plays a key role in our circadian rhythm: daylight contains high levels of blue light, suppressing melatonin production and keeping us awake and sharp.
Colour in everyday life
Colour is not a passive backdrop. It is a continuous stream of environmental signals influencing your attention, choices and mood. Once you realise that colour is an interplay between physics outside you and biology within you, you begin to see your surroundings differently. The choices you make regarding the clothes you wear, the decoration of your room or a walk in the forest are direct ways to influence how you feel. Take a moment to observe the colours around you more consciously. You are not simply looking at a hue; you are observing millions of years of biological evolution in action.