Nowadays in the West, the colour blue is immensely popular. From the colour of jeans to the UN and EU flags, blue is a positive and consensual colour. However, it has not always been the case. In Ancient Rome blue was not a highly valued colour. And in early Christianity, Mary was not wearing a blue mantle. It is during the 12thcentury that in Europe blue progressively became a colour symbolically associated with the spiritual and divine. This lecture retraces the story of blue in Western arts, from Antiquity to the present. We will reflect upon the changing meaning(s) given to this colour. e will also evoke the different materials used to create a whole range of blue pigments: from ultramarine and cobalt to Prussian blue and Yves Klein Blue.