This post looks at how human vision has evolved and the different wavelengths of different colours. It shows both the biology and the psychology of colours and the impact on humans.
How Humans have Evolved to see Colour
It is only in the past decade that scientists have discovered how our vision has evolved by tracing back our evolutionary pathway. 90 million years ago our mammal ancestors were nocturnal and saw in black and white with UV-sensitive and red-sensitive colour vision. Fast forward 60 millions years and UV-vision was lost, replaced with vision sensitive to blue pigment. The research shows that humans needed seven different molecular and environmental changes spread over millions of years for this to happen. It is likely that UV-vision was lost because it wasn’t needed, but that the ability to distinguish red fruits and berries against their green background was important to our primate fore-bearers.
Today most mammals except for primates have relatively poor colour vision. Human eyes have 127 million light-sensitive cells in the back of the retina. The rod cells provide information to the visual cortex about tone and shade, and the cone cells detect colour and detail. We have binocular vision – meaning data from each eye is fed into the brains visual centre to produce an image that has height, width and depth.
“Many genetic mutations in visual pigments, spread over millions of years, were required for humans to evolve from a primitive mammal with a dim, shadowy view of the world into a greater ape able to see all the colors in a rainbow”
Science Daily, 2014
Different colours operate at different wavelengths. When light from the sun meets a coloured object, the object absorbs the wavelengths that are the same as it’s own and they reflect the rest. When light reaches the human eye, the wavelengths in turn reach us differently. They are converted to electric impulses that communicate with our brains. Specifically the part of the brain called the hypothalamus, which influences are hormones.
It’s easy to remember the wavelengths of each colour by imagining a rainbow. The outer bow is red and has the longest “stretched” wavelength. The shortest bow and wavelength is violet. Green sits in the middle.
White (as discovered by Newton) happens when all colours converge – which is why we often see light as white. Black is the absence of colour – and not a colour in itself.
“But the most surprising, and wonderful composition was that of Whiteness. There is no one sort of Rays which alone can exhibit this. ‘Tis ever compounded, and to its composition are requisite all the aforesaid primary Colours, mixed in a due proportion”.
Sir Isaac Newton
The Biology of Colour
When we see colours our visual centre converts the information into electrical impulses to the hypothalamus – located in the centre of our head.
The hypothalamus specifically controls our hormones through the pituitary gland. Hormones are chemical messages which travel through our blood. They effect:
- Growth and development
- Brain and nervous system function
- Water regulation and appetite
- Metabolism and sleep
- Sex drive and reproductive health
The biological impacts of colours are below. It is also important to observe where they appear in nature.
Red: The colour of blood, injury, but also berries and fruit. It has the longest wavelength and grabs our attention as it appears nearer than it is – although not technically the most visible. It has a strong physical effect, raising our pulse rate and can make us feel that time is passing quickly.
Orange: Orange has the second longest wavelength and is both physically and emotionally stimulating – it has an effect on our appetite for food, warmth and sex.
Yellow: Yellow has a relatively long wavelength – but stimulates the emotional rather than the physical. It is the strongest colour psychologically and can left our spirits and self esteem, when used correctly. It is the colour of spring flowers.
Green: A mid wave-length colour at the centre of the spectrum, when we see green there is little adjustment needed by our eye. It therefore provokes rest, harmony and calm. Much of the world is green – and it is a reassuring colour indicating the presence of water.
Blue: Blue impacts us mentally rather than physically or emotionally. It soothes us, aids concentration. Blue objects recede from us visually. It is the colour of daytime sky.
Purple/Violet: With the shortest wavelength – the last visible to humans – violet or purple provokes deep thought and contemplation. it is the colour of the night sky.
Black and White: Black has no specific wavelength as it is not technically a colour. However it’s effect on humans is considerable. It absorbs light and energy and acts as a shroud. White is all colours and is total reflection – so will reflect the whole spectrum into our eyes – it therefore can also be seen as a barrier. It is hard to look at.
“I found I could say things with color and shapes that I couldn’t say any other way.”
The Psychology of Colour
In addition to the scientific impact colours have on our bodies, there are also cultural and psychological influences at play. Sometimes they are the same, but often they are surprisingly different in various places around the world. In the UK a bride will very often be dressed in white – a colour associated with purity, yet in India she will usually be dressed in auspicious red. Red is a very lucky colour in China, yet in other countries it can mean danger.
You cannot argue with the science of colour – green is calming, red raises the pulse, orange provokes hunger, etc, but in my design work, I consider carefully what colour mean to individuals and families. Generally speaking, in the part of the world I live in, the following psychologies of colours exist – these are clearly part based on science and part based on culture. (source: Colour Effects):
- Red: Positive: Physical courage, strength, warmth, energy, basic survival, ‘fight or flight’, stimulation, excitement. Negative: Defiance, aggression, strain.
- Orange: Positive: Physical comfort, food, warmth, security, sensuality, passion, abundance, fun. Negative: Deprivation, frustration, frivolity, immaturity.
- Yellow: Positive: Optimism, confidence, self-esteem, extroversion, emotional strength, friendliness, creativity. Negative: Irrationality, fear, emotional fragility, depression, anxiety.
- Green: Positive: Harmony, balance, refreshment, universal love, rest, restoration, reassurance, environmental awareness, equilibrium, peace. Negative: Boredom, stagnation, blandness.
- Blue: Positive: Intelligence, communication, trust, efficiency, serenity, duty, logic, coolness, reflection, calm. Negative: Coldness, aloofness, lack of emotion, unfriendliness.
- Purple/Violet: Positive: Spiritual awareness, containment, vision, luxury, authenticity, truth, quality. Negative: Introversion, decadence, suppression, inferiority.
- Black: Positive: Sophistication, glamour, security, emotional safety, efficiency, substance. Negative: Oppression, coldness, menace, heaviness.
- White: Positive: Hygiene, sterility, clarity, purity, cleanness, simplicity, sophistication, efficiency. Negative: Sterility, coldness, barriers, unfriendliness, elitism.
Grey has no colour psychology or science attached to it. It is neutral – and best considered as a shade of white or a shade of black and used only to set off other colours. Likewise, whilst studying colour theory at university, I came to understand that all colours are brown, in that brown is made up of yellow, red and blue: There is always a small amount of blue and yellow in any red; a small amount of red and blue in any yellow; and a small amount of yellow and red in any blue. Brown therefore takes on the qualities of its most dominant contributor. Very dark browns may take on the quality of black.
The scientific impact of colours is significant – and worth taking into account when choosing a colour or a painting for a room – at work or at home. Colour theory has long been applied in hospital design for example. I am interested in the mounting scientific evidence that your environment and what you look at has a direct impact on your health. As an artist interested in healing, I love exploring creating artwork and spaces that aid recovery and stimulate wellbeing.