The science behind colour
Colour is used in nature to ward off predators or to attract mates across many forms of life from plants to reptiles, birds and insects.
Light in the form of electromagnetic radiation of different wavelengths (colours) plays an essential part in the evolution of life on earth. Colour is also the basis of much of the beauty and aesthetic appeal of many works of art or architecture.
Anglers talk about which colour spinner led to their successful catch. Less fortunate are accounts of how too many hunters mistake a fellow hunter for a deer and accidently shoot someone.
The perception of colour and light plays a vital role both for the predator and the prey and often provides benefits to one or other or both.
The colours of many plants, animals and minerals are perceived (seen) through which wavelengths are transmitted and absorbed.
A blue object absorbs red colours and reflects unabsorbed blue wavelengths. Scientists have also used this information to be able to analyse the constituents of stars and galaxies. When materials are heated, their atoms gain energy to form excited highly energetic atoms.
These can then emit light with unique signatures, allowing scientists to understand the composition of these celestial bodies.
As scientists reveal some of these mysteries, others are turning their attention to understanding and making advances in studies involving a very different mechanism of colour production.
The striking colours of many ‘‘iridescent’’ living species are produced in a more complex manner. Iridescence, also called ‘‘goniochromism’’, can be seen in soap bubbles and oil films on water.
When observed from different angles, iridescent or goniochromatic surfaces appear to change colour, very different from looking at a red object from a different angle. Butterfly wings, soap bubbles, seashells and certain minerals display this property commonly referred to as containing ‘‘structural’’ colour.
Structural colour (causing colours to change, or the intensity of a single colour to vary with changing angle) enhances the mating and survival success of a species.
By stacking a number of microlayers, colours can be combined to produce an enhanced iridescence or to cancel colours to create more diffuse colour when observed from different angles.
This is in addition to the ability to produce different colours. By alternating layers of chitinous material and air, peacocks and butterflies are able to produce the beautiful, strikingly well defined colours to be found on a peacock’s feather or a butterfly wing.
Scientists have found that, in a bird of paradise, Parotia lawesi, the barbules of the feathers of its brightly coloured breast patch are V-shaped. This creates microstructures that reflect two different colours very strongly, bright blue-green and vibrant orange-yellow. During slight movements in courtship, the colour switches between these two colours to attract a female. This unique arrangement of microstructure arrangement and use is thought to have become sexually selected through the process of evolution.
Yet another form of colour is found in some squid species.
The configuration of chromatophore proteins in these squid species is controlled by electric charge. In the absence of the charge, the proteins pack closely together, causing colourful reflections.
In the presence of charge, the increased distance between proteins result in less visibility, an important feature in the squid’s survival as it is difficult for a predator to identify it. The squid can thus use colourful display to attract a mate, or it can effectively ‘‘hide’’ by becoming less visible.
Humans have applied these findings to try and manufacture synthetic adaptive camouflage materials for military use. Like a chameleon, a combatant wearer would better be able to blend into their changing environment.
However, this would not be a good idea for human hunting groups.