The colour blue is ever present in our lives. It is the colour of the sky and of the ocean and seas. Yet despite its omnipresence, blue is a historically rare and often expensive material. Many languages did not have a word for blue, or did not have the vocabulary to distinguish blue and green until more recent times. The elusive colour was associated with the rich and the divine across the world. But within the spectrum of blues, the most prized of them were in Asia.