The Science of Attraction

What is Color?

The colors of many tropical butterflies are difficult to describe, because they appear to shift with every flutter. This is the magic of iridescence, a gradual change in color resulting from the interaction between different forms of reflected light.

Detail of the wing of a Papilio blumei butterfly, taken with a SEM. Photo by Rogelio Moreno
What living things perceive as colors are in reality waves of light energy reflected from the objects they see. Different colors are associated with specific wavelengths, and which of these are visible depends on the types of receptors in the eye. The colors of an organism are determined by pigments in the cells, or by the structure of its external anatomy. Pigments are cellular substances that absorb certain forms of light while reflecting others. Carotenoids, for instance, reflect light ranging from yellow to red. On the other hand, the shape and arrangement of microscopic surface structures, in scales and feathers for example, can bend light to produce structural colors. These can change depending on the viewing angle, and are responsible for the quality of iridescence.


Morpho zephyritis. Photo by Mercedes Lisón Martín, EducaMadrid mediateca