Sangeetha Pulapaka

Colour has played a major role in the development of civilizations and has acquired important cultural functions as one of the essential ways of human self-expression and affectation. Colours produce aesthetic stimulation, which is reflected in art forms. All this emphasizes the outstanding role of colour in human development, and colouring substances in the form of pigments have thus always been used by mankind as they became available. Evidence of the earliest cultural activities of mankind applying pigments are wall paintings, which used colours available from soil.

 Applying pigments are wall paintings, which used colours available from soil. Quite remarkably the colour blue is absent from them. Blue pigments are not ubiquitous, in the sense that the earth's surface soil normally does not provide them. Mineral blues are found in nature almost exclusively in mines, which makes them difficult to obtain. Given this circumstance and the fact that blue minerals are rare meant that even later civilizations were sometimes lacking this colour. When some of the rare blue minerals were discovered, man made immediate use of them and attributed high value to them. However, due to the shortage of blue pigments, man at a certain appropriate stage took advantage of his skills and began to manufacture it.

This is a picture of the pigment-derived leaf color of decades-old specimen of the African perennial Pollia condensata. Though the pigment of the leaf faded, the fruit still maintains its intense mettalic-blue indescence.

Blue color is rare in both the animal and plant Kingdoms in general. In animals, blue coloring is generated through structural optic light effects, and not through colored pigments. In the few blue-colored plants, the blue color is generated by blue pigment, namely anthocyanins. The reason for the scarcity of blue pigments remains unknown.